U.S. patent application number 14/911494 was filed with the patent office on 2016-06-30 for headphone and acoustic characteristic adjusting method.
This patent application is currently assigned to SONY CORPORATION. The applicant listed for this patent is SONY CORPORATION. Invention is credited to Yuusuke OOSATO, Takahiro SUZUKI.
Application Number | 20160192065 14/911494 |
Document ID | / |
Family ID | 52468207 |
Filed Date | 2016-06-30 |
United States Patent
Application |
20160192065 |
Kind Code |
A1 |
OOSATO; Yuusuke ; et
al. |
June 30, 2016 |
HEADPHONE AND ACOUSTIC CHARACTERISTIC ADJUSTING METHOD
Abstract
[Object] To make it possible to improve an acoustic
characteristic. [Solution] There is provided a headphone including
a driver unit that includes a diaphragm, a housing that
accommodates the driver unit, and forms a sealed-type front-face
air chamber spatially blocked from an outside except for an opening
for sound output on a front face side provided with the diaphragm
of the driver unit, and an acoustic tube whose end is directly
connected to a first ventilation hole provided in a frame of the
driver unit, and that spatially connects a driver-unit rear-face
air chamber formed between the frame and the diaphragm with the
outside of the driver unit via a tube.
Inventors: |
OOSATO; Yuusuke; (Tokyo,
JP) ; SUZUKI; Takahiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SONY CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
SONY CORPORATION
Tokyo
JP
|
Family ID: |
52468207 |
Appl. No.: |
14/911494 |
Filed: |
July 2, 2014 |
PCT Filed: |
July 2, 2014 |
PCT NO: |
PCT/JP2014/067668 |
371 Date: |
February 11, 2016 |
Current U.S.
Class: |
381/378 ;
381/380 |
Current CPC
Class: |
H04R 1/1008 20130101;
H04R 1/1016 20130101; H04R 2460/11 20130101; H04R 1/2826 20130101;
H04R 1/2819 20130101; H04R 11/02 20130101; H04R 1/2857
20130101 |
International
Class: |
H04R 1/28 20060101
H04R001/28; H04R 1/10 20060101 H04R001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2013 |
JP |
2013-167754 |
Claims
1. A headphone comprising: a driver unit that includes a diaphragm;
a housing that accommodates the driver unit, and forms a
sealed-type front-face air chamber spatially blocked from an
outside except for an opening for sound output on a front face side
provided with the diaphragm of the driver unit; and an acoustic
tube whose end is directly connected to a first ventilation hole
provided in a frame of the driver unit, and that spatially connects
a driver-unit rear-face air chamber formed between the frame and
the diaphragm with the outside of the driver unit via a tube.
2. The headphone according to claim 1, wherein, in an acoustic
equivalent circuit of the headphone, a parallel resonance
generating anti-resonance at a predetermined resonance frequency is
formed by an acoustic capacitor corresponding to a capacitance
component of the driver-unit rear-face air chamber, and an acoustic
inductance corresponding to an inductance component of the acoustic
tube.
3. The headphone according to claim 2, wherein the resonance
frequency is determined at least based on a value of the acoustic
inductance and a value of the acoustic capacitor.
4. The headphone according to claim 3, wherein, in the frame of the
driver unit, a second ventilation hole spatially connecting the
driver-unit rear-face air chamber with the outside of the driver
unit is provided at a position different from a position of the
first ventilation hole, wherein, in the second ventilation hole, a
ventilation resistance body acting as resistance in the acoustic
equivalent circuit of the headphone is provided, and wherein a
sound pressure level of the headphone in a predetermined frequency
band is determined at least based on a value of an acoustic
resistor corresponding to a resistance component of the ventilation
resistance body in the acoustic equivalent circuit.
5. The headphone according to claim 4, wherein the sound pressure
level of the headphone in the predetermined frequency band is
determined at least based on the value of the acoustic capacitor
corresponding to the capacitance component of the driver-unit
rear-face air chamber, the value of the acoustic inductance
corresponding to the inductance component of the acoustic tube in
the acoustic equivalent circuit, and the value of the acoustic
resistor.
6. The headphone according to claim 3, wherein the value of the
acoustic inductance is determined according to a length and an
inner cross-sectional area of the acoustic tube, and wherein the
length and the inner cross-sectional area of the acoustic tube is
set in a manner that the resonance frequency is a value between 200
(Hz) to 400 (Hz).
7. The headphone according to claim 6, wherein, in the acoustic
tube, a ratio of the length to the inner cross-sectional area is 76
(1/mmm) to 1124 (1/mm).
8. The headphone according to claim 1, wherein the acoustic tube
includes a tubular member formed of a material having
flexibility.
9. The headphone according to claim 8, wherein the frame of the
driver unit has a disk shape, and wherein the tubular material is
arranged along a circumference direction of the disk shape.
10. The headphone according to claim 1, wherein the acoustic tube
is formed by arranging a rod-like member whose face has a groove
formed toward a longitudinal direction in a manner that the face on
which the groove is formed is closely fitted to one face on a rear
face side opposite to the front face side of the frame of the
driver unit, and at least one part of the groove is in contact with
the first ventilation hole.
11. The headphone according to claim 10, wherein the frame of the
driver unit has a disk shape, and wherein the rod-like member is
curved in an arch shape to have curvature equal to or less than a
circumference of the disk-like shape, and arranged along a
circumference direction of the disk-like shape.
12. The headphone according to claim 1, wherein the driver unit is
a dynamic driver unit.
13. The headphone according to claim 12, wherein a balanced
armature driver unit is further accommodated within the
housing.
14. The headphone according to claim 1, wherein the acoustic tube
spatially connects the driver-unit rear-face air chamber with the
outside of the housing via the tube.
15. The headphone according to claim 14, wherein a rear-face air
chamber as a space surrounded by the housing and the driver unit is
formed on a rear face side opposite to the front face side of the
driver unit, wherein an opening spatially connecting the rear-face
air chamber with the outside of the housing is provided in the
housing, and wherein the other end of the acoustic tube is provided
within the rear-face air chamber.
16. The headphone according to claim 14, wherein the other end of
the acoustic tube is provided in the outside of the housing.
17. The headphone according to claim 1, wherein a sound guiding
tube as a tubular part projecting toward the outside is formed in
one part of a region constituting the front-face air chamber of the
housing, wherein the opening for sound output is provided in a tip
end part of the sound guiding tube, and wherein the headphone is a
canal-type earphone in which the tip end part of the sound guiding
tube is inserted into an external auditory canal of a user.
18. The headphone according to claim 1, wherein the headphone
includes a pair of the housings that accommodate the driver unit,
wherein the pair of the housings are coupled with each other by a
support member curved in an arch shape, and wherein the headphone
is an overhead-type headphone worn on a head of a user with the
support member in a manner that the opening for sound output of the
housing faces an ear of the user.
19. An acoustic characteristic adjusting method comprising:
accommodating a driver unit that includes a diaphragm within a
hosing, and forming a sealed-type front-face air chamber spatially
blocked from an outside except for an opening for sound output,
between the housing and a front face side provided with the
diaphragm of the driver unit; and providing an acoustic tube whose
end is directly connected to a first ventilation hole provided in a
frame of the driver unit, and that spatially connects a driver-unit
rear-face air chamber formed between the frame and the diaphragm
with the outside of the driver unit via a tube.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a headphone and an
acoustic characteristic adjusting method.
BACKGROUND ART
[0002] Typically in a headphone, a driver unit disposed within a
housing drives a diaphragm according to an audio signal to thereby
vibrate air to generate sound. Here, it is known that an acoustic
characteristic of the headphone depends on a structure within the
housing. Specifically, the acoustic characteristic of the headphone
can vary according to the volume of a space provided within the
housing, a size of a ventilation hole, which can be a passage of
air, formed within the housing, or the like. Therefore, a number of
techniques on the structure within the housing have been
proposed.
[0003] There has been disclosed a sealed-type canal-type earphone
in which a space spatially blocked from the outside, except for an
opening for outputting sound toward the outside, is formed between
a housing and a front face side as a side provided with a diaphragm
of a driver unit (see, for example, Patent Literature 1).
Furthermore, there has been disclosed a technique for improving an
acoustic characteristic by providing a tubular duct unit, which
spatially connects between the inside and the outside of a housing,
on a rear side of the housing as a side opposite to the side
provided with a diaphragm of a driver unit (see, for example,
Patent Literature 2).
CITATION LIST
Patent Literature
[0004] Patent Literature 1: JP 2007-189468A [0005] Patent
Literature 2: JP H4-227396A
SUMMARY OF INVENTION
Technical Problem
[0006] However, requirements to an acoustic characteristic, such as
a desire to emphasize an output of sound in a low range, differ
depending on the intended use of a headphone. Therefore, a desired
acoustic characteristic is not always obtained by applying the
techniques described in Patent Literature 1 and Patent Literature 2
to the headphone.
[0007] Accordingly, the present disclosure proposes a novel and
improved headphone and acoustic characteristic adjusting method,
capable of further improving an acoustic characteristic.
Solution to Problem
[0008] According to the present disclosure, there is provided a
headphone including: a driver unit that includes a diaphragm; a
housing that accommodates the driver unit, and forms a sealed-type
front-face air chamber spatially blocked from an outside except for
an opening for sound output on a front face side provided with the
diaphragm of the driver unit; and an acoustic tube whose end is
directly connected to a first ventilation hole provided in a frame
of the driver unit, and that spatially connects a driver-unit
rear-face air chamber formed between the frame and the diaphragm
with the outside of the driver unit via a tube.
[0009] According to the present disclosure, there is provided an
acoustic characteristic adjusting method including: accommodating a
driver unit that includes a diaphragm within a hosing, and forming
a sealed-type front-face air chamber spatially blocked from an
outside except for an opening for sound output, between the housing
and a front face side provided with the diaphragm of the driver
unit; and providing an acoustic tube whose end is directly
connected to a first ventilation hole provided in a frame of the
driver unit, and that spatially connects a driver-unit rear-face
air chamber formed between the frame and the diaphragm with the
outside of the driver unit via a tube.
[0010] According to the present disclosure, an acoustic tube
spatially connecting, via the tube, between the driver-unit
rear-face air chamber and the outside of the driver unit is
provided, so that a parallel resonance circuit by a capacitor
corresponding to the volume of the driver-unit rear-face air
chamber and an inductance corresponding to an inductance component
to a flow of air in the acoustic tube, is formed in an acoustic
equivalent circuit. Therefore, it becomes possible to adjust a
sound pressure level characteristic by using anti-resonance in the
parallel resonance circuit. The increase in parameters for
adjusting the sound pressure level characteristic makes it easy to
realize the desired sound pressure level characteristic and makes
it possible to further improve an acoustic characteristic.
Advantageous Effects of Invention
[0011] As described above, according to the present disclosure, it
becomes possible to further improve an acoustic characteristic.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a schematic diagram illustrating a schematic
configuration of a headphone according to an embodiment of the
present disclosure.
[0013] FIG. 2 is a diagram illustrating an acoustic equivalent
circuit of the headphone of FIG. 1.
[0014] FIG. 3 is a graphic diagram illustrating a sound pressure
level characteristic of the headphone according to the present
embodiment.
[0015] FIG. 4 is a cross-sectional diagram illustrating a
configuration of the headphone according to an embodiment of the
present disclosure.
[0016] FIG. 5 is an exploded perspective diagram of a driver unit
and an acoustic tube of FIG. 4.
[0017] FIG. 6 is a graphic diagram illustrating a relationship
between a resonance frequency fh of anti-resonance, and a length L
of the acoustic tube, an inner cross-sectional area S of the
acoustic tube and a volume V of a driver-unit rear-face air
chamber.
[0018] FIG. 7 is a graphic diagram illustrating a relationship
between a resonance frequency fh of anti-resonance, and a length L
of the acoustic tube, an inner cross-sectional area S of the
acoustic tube and a volume V of a driver-unit rear-face air
chamber.
[0019] FIG. 8A is an appearance diagram illustrating a
configuration of a headphone according to a modification of an
embodiment of the present disclosure.
[0020] FIG. 8B is an appearance diagram illustrating a
configuration of a headphone according to a modification of an
embodiment of the present disclosure.
[0021] FIG. 8C is an appearance diagram illustrating a
configuration of a headphone according to a modification of an
embodiment of the present disclosure.
[0022] FIG. 8D is an appearance diagram illustrating a
configuration of a headphone according to a modification of an
embodiment of the present disclosure.
[0023] FIG. 9A is a diagram virtually transparently illustrating a
part of a housing and illustrating a state of structural members
within the housing, in the headphone of FIG. 8A.
[0024] FIG. 9B is a diagram virtually transparently illustrating a
part of a housing and illustrating a state of structural members
within the housing, in the headphone of FIG. 8B.
[0025] FIG. 9C is a diagram virtually transparently illustrating a
part of a housing and illustrating a state of structural members
within the housing, in the headphone of FIG. 8C.
[0026] FIG. 10A is a cross-sectional diagram of the headphone of
FIG. 8A.
[0027] FIG. 10B is a cross-sectional diagram of the headphone of
FIG. 8A.
[0028] FIG. 11 is an explanatory diagram for explaining a structure
of an acoustic tube according to the present modification.
[0029] FIG. 12A is a schematic diagram illustrating a state of the
headphone according to the present modification, being worn on a
user.
[0030] FIG. 12B is a schematic diagram illustrating a state of the
headphone according to the present modification, being worn on a
user.
DESCRIPTION OF EMBODIMENTS
[0031] Hereinafter, (a) preferred embodiment(s) of the present
disclosure will be described in detail with reference to the
appended drawings. In this specification and the drawings, elements
that have substantially the same function and structure are denoted
with the same reference signs, and repeated explanation is
omitted.
[0032] Note that description will be provided in the following
order.
1. Outline of Embodiment of Present Disclosure
2. Configuration of Headphone
3. Acoustic Characteristic Adjusting Method
4. Modification
5. Complement
<1. Outline of Embodiment of Present Disclosure>
[0033] With reference to FIG. 1 to FIG. 3, an outline of an
embodiment of the present disclosure will be described. First, with
reference to FIG. 1, a schematic configuration of a headphone
according to the present embodiment will be described. Next, with
reference to FIG. 2, an acoustic equivalent circuit of the
headphone according to the present embodiment will be described.
Further, with reference to FIG. 3, an acoustic characteristic
realized by the present embodiment will be described
qualitatively.
[0034] First, with reference to FIG. 1, a schematic configuration
of a headphone according to an embodiment of the present disclosure
will be described. FIG. 1 is a schematic diagram illustrating the
schematic configuration of the headphone according to an embodiment
of the present disclosure. Referring to FIG. 1, a headphone 10
according to the present embodiment includes a driver unit 110, and
a housing 140 accommodating the driver unit 110 therein. FIG. 1
illustrates a cross section passing through a substantial center of
the driver unit 110, of the headphone 10. Further, in FIG. 1, for
convenience, only primary structural members in the present
embodiment, of structural members of the headphone 10 are
schematically illustrated. Further, in FIG. 1, in order to indicate
a correspondence between the structural members of the headphone 10
and elements of the acoustic equivalent circuit of FIG. 2, symbols
of the elements in the acoustic equivalent circuit are added to
signs with which the structural members are partially denoted.
[0035] The driver unit 110 has a frame 111, a diaphragm 112, a
magnet 113, a plate 114, and a voice coil 115. The frame 111 has a
substantially disk shape, and on one face side of the disk shape,
arranged are the magnet 113, the plate 114, the voice coil 115 and
the diaphragm 112. The frame 111 has a projection in its
substantial center portion, the projection being projected to a
side opposite to the side provided with the magnet 113, the plate
114, the voice coil 115 and the diaphragm 112. The magnet 113, the
plate 114, and the voice coil 115 have a cylindrical shape, and are
arranged in the inside of the projection substantially
concentrically with the frame 111. The magnet 113 is held between
the frame 111 and the plate 114. The voice coil 115 is arranged
further on the outer circumferential side of the magnet 113 and the
plate 114. The diaphragm 112 is provided so as to cover one face of
the frame 111, and whose partial region is connected to the voice
coil 115. When the voice coil 115 is driven within a magnetic field
generated by the magnet 113 according to an audio signal supplied
from the outside, for example, by a cable (not shown) or the like,
the diaphragm 112 vibrates in its thickness direction. Here, the
audio signal is an electric signal on which audio information is
superimposed. The diaphragm 112 vibrates according to the audio
signal to thereby generate coarseness or denseness in ambient air
to generate sound corresponding to the audio signal.
[0036] Here, in the following description, a center axis direction
in the disk shape of the driver unit 110 is referred to as a z-axis
direction. Further, a side provided with the diaphragm 112 when
viewed from the driver unit 110 is referred to as a front face
side, and a direction of the front face side in the z-axis
direction is referred to as a positive direction or a front face
direction of the z-axis direction. Further, a side opposite to the
front face side is referred to as a rear face side, and a direction
of the rear face side in the z-axis direction is referred to as a
negative direction or a rear face direction of the z-axis
direction. Further, two directions perpendicular to each other
within a plane perpendicular to the z-axis direction are referred
to as an x-axis direction and a y-axis direction.
[0037] In the present embodiment, the voice coil 115 has a
cylindrical shape. In the diaphragm 112, a region located on an
inner side of the voice coil 115 is referred to also as a dome
part, and a region located on an outer side of the voice coil 115
is referred to also as an edge part. Similarly, in the frame 111, a
region located on the inner side of the voice coil 115 (a region
corresponding to the projection) is referred to also as a dome
part, and a region located on the outer side of the voice coil 115
(a region corresponding to a flange part in the outer circumference
of the projection) is referred to also as an edge part. In the
following description, for convenience, also for a space between
the frame 111 and the diaphragm 112 (hereinafter referred to as a
driver-unit rear-face air chamber 118), a space formed on the inner
side of the voice coil 115 will be referred to as a dome part, and
a space formed on the outer side of the voice coil 115 will be
referred to as an edge part. In the frame 111 of the driver unit
110, provided are ventilation holes 116a, 116b and 116c penetrating
the frame 111 in the z-axis direction, and the driver-unit
rear-face air chamber 118 is spatially connected to a space on a
rear side of the driver unit 110 (that is, the outside of the
driver unit 110) through the ventilation holes 116a, 116b and 116c.
In the example shown in FIG. 1, the ventilation hole 116b is formed
in a substantial center of the frame 111, and spatially connects
the dome part of the driver-unit rear-face air chamber 118 with the
outside of the driver unit 110. Further, the ventilation holes 116a
and 116c are formed at positions radially shifted from the center
of the frame 111 by a predetermined distance, and spatially connect
the edge part of the driver-unit rear-face air chamber 118 with the
outside of the driver unit 110.
[0038] In the ventilation holed 116b and 116c, ventilation
resistance bodies 117a and 117b are provided so as to block the
holes. The ventilation resistance bodies 117a and 117b are formed
of, for example, compressed urethane, a nonwoven fabric, or the
like, and acts as a resistance component to a flow of air. However,
a material of the ventilation resistance bodies 117a and 117b is
not limited thereto, and another material may be used if it can
give predetermined resistance to a flow of air.
[0039] To the ventilation hole 116a, one end of the acoustic tube
150 is connected. The acoustic tube 150 is a tubular member
spatially connecting the driver-unit rear-face air chamber 118 with
the outside of the driver unit 110 via the tube. Here, the acoustic
tube 150 is formed so as to have such a length and inner
cross-sectional area that can be a predetermined inductance
component and a predetermined resistance component to a flow of air
passing through the acoustic tube 150. Here, the inner
cross-sectional area of the acoustic tube 150 is a cross-sectional
area of the inside of the tube defined by an inner diameter of the
acoustic tube 150. A detailed configuration and shape of the
acoustic tube 150 will be described in <2. Configuration of
Headphone> described below and <3. Acoustic Characteristic
Adjusting Method> described below.
[0040] Note that, in the example shown in FIG. 1, the ventilation
hole 116a to which one end of the acoustic tube 150 is directly
connected is provided in a region corresponding to the edge part of
the driver-unit rear-face air chamber 118, and the ventilation
holes 116b and 116c provided with the ventilation resistance bodies
117a and 117b are provided in regions corresponding to the dome
part and the edge part of the driver-unit rear-face air chamber
118, respectively, but the positions provided with the ventilation
holes 116a, 116b and 116c are not limited thereto. In the present
embodiment, for example, one end of the acoustic tube 150 may be
directly connected to the ventilation hole 116b, and the acoustic
tube 150 may spatially connect the dome part of the driver-unit
rear-face air chamber 118 with the outside of the driver unit 110
via the tube. The formation position of the ventilation hole to
which one end of the acoustic tube 150 is connected, in the frame
111, may be optionally set so that the acoustic tube 150 and the
other structural members are efficiently arranged within the
housing 140.
[0041] Furthermore, the driver unit 110 according to the present
embodiment may be a so-called dynamic-type driver unit. Further,
the driver unit 110 according to the present embodiment may have a
configuration similar to that of an existing typical dynamic-type
driver unit except for being provided with the acoustic tube 150.
For example, to arrangement positions of the frame 111, the
diaphragm 112, the magnet 113, the plate 114 and the voice coil 115
and a driving method of the driver unit 110, arrangement positions
and a driving method of these members in the typical dynamic-type
driver unit may be applied. However, the driver unit 110 according
to the present embodiment is not limited to the typical
dynamic-type driver unit, and may be a so-called balanced
armature-type driver unit (BA-type driver unit). Even when the
acoustic tube 150 is provided in the existing typical dynamic-type
driver unit, an effect similar to that of a dynamic-type driver
unit to be described later can be obtained.
[0042] The housing 140 accommodates the driver unit 110 therein. On
a front face side of the driver unit 110, formed is a front-face
air chamber 125 formed by the driver unit 110 and the housing 140.
Further, on a rear face side of the driver unit 110, formed is a
rear-face air chamber 132 formed by the driver unit 110 and the
housing 140.
[0043] The housing 140 may be configured by a plurality of members.
In the example shown in FIG. 1, the housing 140 is formed by
joining a front housing 120 covering the front face side of the
driver unit 110 and a rear housing 130 covering the rear face side
of the driver unit 110 together. Note that the present embodiment
is not limited thereto, and the housing 140 may be configured by
three or more members.
[0044] In a partition wall of the front housing 120, provided are
openings 121 and 122 spatially connecting the inside of the housing
140 with the outside. The opening 121 is an opening for outputting
sound to the outside (that is, an opening for sound output). Air
within the front-face air chamber 125 can be outputted to the
outside as sound via the opening 121. In a partial region of the
front housing 120, formed is a sound guiding tube 124 as a tubular
part provided so as to project toward the outside, and the opening
121 is provided in a tip end part of the sound guiding tube 124.
When a user listen to sound, the tip end part of the sound guiding
tube 124 is inserted into the external auditory canal of the user.
In this manner, in the present embodiment, the headphone 10 may be
a so-called canal-type earphone. Note that an earpiece (not shown)
for allowing the sound guiding tube 124 to be closely fitted to the
inner wall of the external auditory canal of the user may be
provided in the outer circumference of the tip end part of the
sound guiding tube 124. Further, an equalizer (not shown) as a
ventilation resistance body may be provided inside the sound
guiding tube 124. It is possible to adjust sound quality such as
reducing an output of sound in a specific frequency band by
optionally setting a material and a shape of the equalizer.
[0045] In the opening 122, a ventilation resistance body 123 is
provided so as to block the hole. The ventilation resistance body
123 has a function similar to that of the ventilation resistance
bodies 117a and 117b. In the present embodiment, however, the
ventilation resistance body 123 has a material and a shape selected
so as to substantially block air. In this manner, in the present
embodiment, the front-face air chamber 125 may be spatially blocked
from the outside with respect to a flow of air except for the
opening 121. In the following description, the front-face air
chamber 125 formed so as to be blocked from the outside with
respect to a flow of air except for the opening 121 for sound
output is referred to also as a sealed-type front-face air chamber
125. Further, the headphone 10 having the sealed-type front-face
air chamber 125 is referred to also as the sealed-type headphone
10.
[0046] In a partition wall of the rear housing 130, provided is an
opening 131 spatially connecting the inside of the housing 140 with
the outside. In the present embodiment, the opening 131 is formed
so as to have such a size that it can be almost no resistance to a
flow of air. In this manner, in the present embodiment, the
rear-face air chamber 132 is connected to a space outside the
housing 140 via the opening 131 while resistance to a flow of air
does not almost exist. Here, in the example shown in FIG. 1, one
end of the acoustic tube 150 is directly connected to the
ventilation hole 116a provided in the frame 111, and the other end
is provided within the rear-face air chamber 132. However, as
described above, in the present embodiment, the rear-face air
chamber 132 is connected to the outside of the housing 140 while
resistance to a flow of air does not almost exist. Therefore, in
the present embodiment, from a view point of an acoustic
characteristic, the acoustic tube 150 can be considered to
spatially connect the driver-unit rear-face air chamber 118 with
the outside of the housing 140. Therefore, in the present
embodiment, the other end of the acoustic tube 150 may be provided
within the rear-face air chamber 132, or may be provided outside
the housing 140. In any case, it is possible to obtain the same
acoustic characteristic.
[0047] With reference to FIG. 1, the schematic configuration of the
headphone 10 according to the present embodiment has been described
above. Next, with reference to FIG. 2, an acoustic equivalent
circuit of the headphone 10 of FIG. 1 will be described. FIG. 2 is
a diagram illustrating the acoustic equivalent circuit of the
headphone 10 of FIG. 1.
[0048] Here, the acoustic equivalent circuit is one obtained by
replacing elements of a mechanical system and an acoustic system
with elements of an electric circuit. In the acoustic equivalent
circuit, its voltage corresponds to sound pressure in the acoustic
system and its current corresponds to particle velocity of air
(that is, a flow of air) in the acoustic system. Therefore, it is
possible to analyze sound pressure of outputted sound in the
headphone 10 by analyzing a voltage in the acoustic equivalent
circuit of the headphone 10. Here, a value obtained by expressing a
ratio of sound pressure to a reference value (for example, a
minimum audible sound pressure value of a human) in a decibel unit
is referred to as a sound pressure level (SPL), which is one
indicator for evaluating an acoustic characteristic. It can be said
that adjusting a sound pressure level characteristic is, that is,
adjusting an acoustic characteristic. It is possible to evaluate an
acoustic characteristic of the headphone 10 by calculating a sound
pressure level from the acoustic equivalent circuit of the
headphone 10.
[0049] With reference to FIG. 2, in an acoustic equivalent circuit
40, a signal source Vs, an inductance Mo, a resistor Ro, and a
capacitor Co are arranged in series. The signal source Vs, the
inductance Mo, the resistor Ro, and the capacitor Co are elements
corresponding to elements of the mechanical system of the driver
unit 110. Specifically, the signal source Vs is an element
corresponding to vibratory force when the diaphragm 112 is vibrated
by the driver unit 110, and is a power supply element for
generating electromotive force in the acoustic equivalent circuit
40. Further, the inductance Mo, the resistor Ro, and the capacitor
Co are elements corresponding to mass, mechanical resistance, and
compliance, respectively.
[0050] Furthermore, in the acoustic equivalent circuit 40, a
resistor R1 and a capacitor C1 are arranged in parallel. Here, the
resistor R1 and the capacitor C1 are elements corresponding to a
flow of air in the front-face air chamber 125. Specifically, the R1
corresponds to a resistance component by the ventilation resistance
body 123 provided in the opening 122 of the front-face air chamber
125. As described above, in the present embodiment, since the
front-face air chamber 125 is a sealed type, the resistor R1 can be
considered to have a sufficiently large value. Further, the
capacitor C1 corresponds to a volume of the front-face air chamber
125.
[0051] Furthermore, in the acoustic equivalent value 40, a resistor
Rb1, a capacitor Cb, an inductance Mb and a resistor Rb2 are
arranged in parallel. Here, the resistor Rb1, the capacitor Cb, the
inductance Mb and the resistor Rb2 are elements corresponding to a
flow of air in the rear-face air chamber 132. Specifically, the
resistor Rb1 corresponds to a resistance component by the
ventilation resistance bodies 117a and 117 b provided in the
ventilation holes 116b and 116c spatially connecting the
driver-unit rear-face air chamber 118 with the rear-face air
chamber 132. In the example shown in FIG. 1, the two ventilation
resistance bodies 117a and 117b are provided in the two ventilation
holes 116b and 116c, respectively, but in the acoustic equivalent
circuit 40, a resistance component by the two ventilation
resistance bodies 117a and 117b is expressed by the one resistor
Rb1. Further, the capacitor Cb corresponds to a volume of the
driver-unit rear-face air chamber 118. Further, the inductance Mb
and the resistor Rb2 correspond to an inductance component and a
resistance component in the acoustic tube 150, respectively. Here,
as described later with reference to FIG. 3, in the present
embodiment, the acoustic characteristic of the headphone 10 is
adjusted by changing a value of the resistor Rb1, the capacitor Cb
and the inductance Mb. In the following, the resistor Rb1, the
capacitor Cb and the inductance Mb are referred to also as an
acoustic resistor, an acoustic capacitor and an acoustic
inductance, respectively.
[0052] Here, paying attention to the capacitor Cb and the
inductance Mb, in the acoustic equivalent circuit 40, it can be
considered that a parallel resonance circuit generating
anti-resonance at a predetermined resonance frequency is formed by
the capacitor Cb and the inductance Mb. In the present embodiment,
it is possible to adjust a sound pressure level in a predetermined
frequency band by generating anti-resonance by the capacitor Cb and
the inductance Mb.
[0053] With reference to FIG. 3, the adjustment of the sound
pressure level using the anti-resonance by the capacitor Cb and the
inductance Mb will be described in detail. FIG. 3 is a graphic
diagram illustrating a sound pressure level characteristic of the
headphone 10 according to the present embodiment. In FIG. 3, a
frequency is indicated in the horizontal axis, and a sound pressure
level is indicated in the vertical axis, and a sound pressure level
characteristic in the headphone 10 obtained from an analysis result
of the acoustic equivalent circuit 40 of FIG. 2 is plotted.
[0054] First, with reference to FIG. 3, a desired acoustic
characteristic in the present embodiment will be described. In the
following description, for convenience, a frequency band of 200 Hz
or less is referred to as a low range, a frequency band of 200 Hz
to 2000 Hz is referred to as a middle range, and a frequency band
of 2000 Hz or more is referred to as a high range. When a frequency
band is divided in this manner, for example, a human voice belongs
to the middle range, and base sound lower than that belongs to the
low range.
[0055] Here, as a typical existing technology, there has been
disclosed a technique for improving an acoustic characteristic by
making a sound pressure level in the low range greater than a sound
pressure level in the middle range. For example, it is known that a
headphone having a sealed-type front-face air chamber (for example,
the canal-type earphone described in Patent Literature 1 described
above) can output sound while maintaining predetermined sound
pressure to a lower frequency band. In this manner, it becomes
possible to realize a sound pressure level characteristic in which
a sound pressure level in the low range is maintained at a higher
value than a sound pressure level in the middle range, by using the
headphone having the sealed-type front-face air chamber. Such a
sound pressure level characteristic in the existing headphone can
be shown, for example, by the dotted curve A shown in FIG. 3.
[0056] Meanwhile, when the sound pressure significantly changes in
a frequency band of the middle range including a human voice, the
human voice sounds like boxy sound for a user listening to the
sound. Therefore, it is desirable that the sound pressure level is
as flat as possible in the middle range. In this manner, it is
thought that as one of ideal acoustic characteristics it has a
sound pressure characteristic in which a sound pressure level is
reduced in a stepwise manner from the low range to the middle range
(hereinafter merely referred to as a "stepwise sound pressure level
characteristic). However, as shown in the curve A, in the sound
pressure level characteristic of the existing headphone, the sound
pressure is gently reduced at a predetermined inclination from the
low range to the middle range. Therefore, the existing headphone
has had a risk that high sound quality for a human voice cannot be
realized, and has had room to improve the sound pressure level in
the middle range.
[0057] Here, in the existing headphone, a sound pressure level in a
predetermined frequency band can be determined at least based on a
value of ventilation resistance between the driver-unit rear-face
air chamber and a space on a rear face side of the driver unit
(that is, corresponding to the resistance components by the
ventilation resistance bodies 117a and 117b of FIG. 1 and the
resistor Rb1 of FIG. 2 in the present embodiment). Specifically, it
is possible to adjust a value of the sound pressure level from the
low range to the middle range by changing a value of the resistor
Rb1 corresponding to the ventilation resistance. Therefore, it is
possible to adjust the sound pressure level in the middle range to
improve a sound characteristic by changing a value of the resistor
Rb1. However, as shown by the arrow in FIG. 3, even when a value of
the resistor Rb1 is changed, a value of the sound pressure level
goes up and down while the inclination in the curve A remains. As
described above, in the existing headphone, it has been difficult
to obtain a stepwise sound pressure level characteristic.
[0058] Meanwhile, in the present embodiment, the parallel resonance
circuit for generating anti-resonance by the capacitor Cb and the
inductance Mb is formed by providing the acoustic tube 150. The
anti-resonance in the acoustic equivalent circuit acts so as to
form a dip in a sound pressure level in the sound pressure level
curve shown in FIG. 3. For example, with reference to FIG. 3, the
curve B having the dip of the sound pressure level in the frequency
band of around 200 (Hz) to 400 (Hz) is shown by the solid line. The
dip corresponds to the anti-resonance generated by the capacitor Cb
and the inductance Mb. Here, a resonance frequency fh of the
anti-resonance is determined at least based on a value of the
capacitor Cb and the inductance Mb. In this manner, in the present
embodiment, it becomes possible to adjust a frequency band where
the resonance frequency fh is included, that is, a frequency band
where the dip of the sound pressure level is formed, by adjusting a
value of the capacitor Cb and the inductance Mb.
[0059] Furthermore, as described above, the driver unit 110
according to the present embodiment may have a configuration
similar to that of the existing typical dynamic-type driver unit
except for being provided with the acoustic tube 150. Therefore,
also in the present embodiment, similarly to the existing
headphone, a sound pressure level in a predetermined frequency band
can be determined at least based on a value of the resistor Rb1.
Specifically, in the present embodiment, it is possible to adjust a
value of the sound pressure level from the low range to the middle
range by changing a value of the resistor Rb1. Therefore, by
adjusting a value of the capacitor Cb and the inductance Mb so that
the resonance frequency fh of the anti-resonance is located between
the low range and the middle range, a value of the sound pressure
level from the low range to the middle range can be a value
obtained by adding a change in value by the resistor Rb1 and a
change in value by the dip formed by the anti-resonance together.
Therefore, a step of the sound pressure level having an inclination
greater than the inclination indicated in the curve A can be formed
in the frequency band where the resonance frequency fh is located,
that is, the frequency band where the dip is formed.
[0060] In this manner, in the present embodiment, the sound
pressure level of the headphone 10 in the predetermined frequency
band can be determined at least based on a value of the capacitor
Cb, a value of the inductance Mb, and a value of the resistor Rb1.
Specifically, the sound pressure level from the low range to the
middle range can be adjusted by the capacitor Cb, the inductance Mb
and the resistor Rb1. Further, in the present embodiment, since the
front-face air chamber 125 is a sealed type, the sound pressure
level characteristic in which the sound pressure level in the low
range is maintained at a value higher than the sound pressure level
in the middle range, can be realized. Therefore, it is possible to
obtain, for example, the stepwise sound pressure level
characteristic described above, by optionally adjusting a value of
the capacitor Cb, the inductance Mb and the resistor Rb1. Further,
in the stepwise sound pressure level characteristic, a sound
pressure level difference between the low range and the middle
range, and a frequency band where a step is located when the sound
pressure level is reduced in a stepwise manner, can be adjusted by
the capacitor Cb, the inductance Mb and the resistor Rb1.
Therefore, for example, a sharp acoustic characteristic having a
large level difference between the low range and the middle range
can be realized.
[0061] In FIG. 3, an example of the stepwise sound pressure level
characteristic obtained in the present embodiment is shown by the
curve C of the broken line. In the sound pressure level
characteristic shown in the curve C, for example, a value of the
capacitor Cb and the inductance Mb can be optionally adjusted so
that the resonance frequency fh is located between 200 (Hz) and 400
(Hz). Further, while the resonance frequency fh is located between
200 (Hz) and 400 (Hz), a value of the resistor Rb1 can be
optionally adjusted so that the sound pressure level is reduced in
a stepwise manner from the low range to the middle range, and the
sound pressure level is nearly flat in the middle range.
[0062] Here, as described above, the capacitor Cb corresponds to
the volume of the driver-unit rear-face air chamber 118, and its
value can be determined by the configuration of the frame 111 and
the diaphragm 112 in the driver unit 110. The inductance Mb
corresponds to the inductance component of the acoustic tube 150,
and its value depends on the shape of the acoustic tube 150. The
smaller the inner cross-sectional area of the acoustic tube 150,
the longer the length, the greater the value of the inductance Mb.
Further, the resistor Rb1 corresponds to the resistance components
by the ventilation resistance bodies 117a and 117b provided in the
ventilation holes 116b and 116c spatially connecting the
driver-unit rear-face air chamber 118 with the rear-face air
chamber 132, and its value depends on the material and the shape of
the ventilation resistance bodies 117a and 117b. For example, the
denser the particles in the material of the ventilation resistance
bodies 117a and 117b, the longer the length of the ventilation
resistance bodies 117a and 117b in a flowing direction of air (the
z-axis direction in the example of FIG. 1), the smaller the
cross-sectional area of the ventilation resistance bodies 117a and
117b, the greater the value of the resistor Rb1. In this manner, in
the present embodiment, it is possible to change a value of the
inductance Mb and the resistor Rb1 and realize a desired sound
pressure level characteristic by changing the configuration of the
frame 111 and the diaphragm 112 in the driver unit 110, the shape
of the acoustic tube 150, and the material and the shape of the
ventilation resistance bodies 117a and 117b.
[0063] In this manner, in the present embodiment, the desired sound
pressure level characteristic is realized by providing the acoustic
tube 150, and optionally setting a value of the capacitor Cb, the
inductance Mb and the resistor Rb1. Therefore, it becomes possible
to adjust and improve the acoustic characteristic.
<2. Configuration of Headphone>
[0064] Next, with reference to FIG. 4, a configuration of the
headphone according to an embodiment of the present disclosure will
be described in more detail. FIG. 4 is a cross-sectional diagram
illustrating the configuration of the headphone according to an
embodiment of the present disclosure. With reference to FIG. 4, a
headphone 20 according to the present embodiment includes a driver
unit 210, and a housing 240 accommodating the driver unit 210
therein. FIG. 4 illustrates a cross section passing through the
substantial center of the driver unit 210, of the headphone 20.
Note that the structural members shown in FIG. 4 are simplified for
description of the present embodiment, and the headphone 20 may
further include structural members not shown, such as a cable for
supplying an audio signal to the driver unit 210. Since the
structural members not shown can be ones already known as
structural members in the existing typical headphone, the detailed
description is omitted.
[0065] Here, the headphone 20 shown in FIG. 4 corresponds to the
headphone 10 described with reference to FIG. 1. In the description
for each structural member of the headphone 20, a correspondence
relationship with each structural member of the headphone 10 of
FIG. 1 will be described. Further, since the corresponding
structural members have functions similar to each other, the
detailed descriptions for ones corresponding to the structural
members already described with reference to FIG. 1 in the
structural members of the headphone 20 are omitted. Further, the
acoustic equivalent circuit of the headphone 20 can be also one
similar to the acoustic equivalent circuit 40 of FIG. 2. Therefore,
similarly to FIG. 1, symbols of the elements in the acoustic
equivalent circuit 40 are added to signs with which the structural
members of the headphone 20 are partially denoted.
[0066] The driver unit 210 has a frame 211, a diaphragm 212, a
magnet 213, a plate 214, and a voice coil 215. The driver unit 210
corresponds to the driver unit 110 of FIG. 1. Further, the frame
211, the diaphragm 212, the magnet 213, the plate 214, and the
voice coil 215 correspond to the frame 111, the diaphragm 112, the
magnet 113, the plate 114, and the voice coil 115 of FIG. 1. A
driver-unit rear-face air chamber 218 is formed between the driver
unit 210 and the diaphragm 212. An element corresponding to
electromotive force when the diaphragm 212 is vibrated corresponds
to the signal source Vs in the acoustic equivalent circuit 40.
Further, mass, mechanical resistance and compliance in the driver
unit 210 corresponds to the inductance Mo, the resistance Ro and
the capacitor Co in the acoustic equivalent circuit 40,
respectively. Further, the volume of the driver-unit rear-face air
chamber 218 corresponds to the capacitor Cb in the acoustic
equivalent circuit 40.
[0067] In the frame 211 of the driver unit 210, provided are
ventilation holes 216a and 216b penetrating the frame 211 in the
z-axis direction. The ventilation holes 216a and 216b correspond to
the ventilation holes 116a and 116b shown in FIG. 1. The
ventilation hole 216a is formed at a position radially shifted from
the center of the frame 211 by a predetermined distance, and
spatially connects the edge part of the driver-unit rear-face air
chamber 218 with the outside of the driver unit 210. Further, the
ventilation hole 216b is formed at the substantial center of the
frame 211, and spatially connects the dome part of the driver-unit
rear-face air chamber 218 with the outside of the driver unit
210.
[0068] In the ventilation hole 216b, a ventilation resistance body
217a is provided so as to block the hole. The ventilation
resistance body 217a corresponds to the ventilation resistance body
117a of FIG. 1. A resistance component to a flow of air, of the
ventilation resistance body 217a corresponds to the resistor Rb1 in
the acoustic equivalent circuit 40.
[0069] Here, a material and a shape of the ventilation resistance
body 217a may be optionally set so as to obtain the desired sound
pressure level characteristic, for example, in consideration of the
sound pressure level characteristic as shown in FIG. 3. More
specifically, as described with reference to FIG. 3, a material and
a shape of the ventilation resistance body 217a can be optionally
set so that a value of the resistor Rb1 for obtaining the stepwise
sound pressure level characteristic can be realized.
[0070] To the ventilation hole 216a, one end of the acoustic tube
259 is connected. An acoustic tube 250 is a member corresponding to
the acoustic tube 150 of FIG. 1. The acoustic tube 250 is a tubular
member spatially connecting the driver-unit rear-face air chamber
218 with the outside of the driver unit 210 via the tube. An
inductance component and a resistance component to a flow of air in
the acoustic tube 250 correspond to the inductance Mb and the
resistor Rb2 in the acoustic equivalent circuit 40,
respectively.
[0071] Here, with reference to FIG. 5, a configuration of the
acoustic tube 250 in the headphone 20 will be described in more
detail. FIG. 5 is an exploded perspective diagram of the driver
unit 210 and the acoustic tube 250 of FIG. 4. In FIG. 5, for
convenience, only the frame 211 of the structural members of the
driver unit 210 is shown, and a state where the acoustic tube 250
is removed from the frame 211 is shown.
[0072] With reference to FIG. 5, the acoustic tube 250 includes an
attachment 251 and a tube 252. The attachment 251 connects the
ventilation hole 216a with one end of the tube 252, and is a
connection member for spatially connecting the driver-unit
rear-face air chamber 218 with the inside of the tube 252. In the
attachment 251, in a region corresponding to the ventilation hole
216a, and a region having one end of the tube 252 attached thereto,
openings are provided, respectively, and these openings are
spatially connected within the attachment 251. Further, a shape and
a formation position of these openings are designed so as to
prevent air from leaking to a space except for the ventilation hole
216a and the inside of the tube 252. In this manner, the use of the
attachment 251 allows the ventilation hole 216a to be spatially
connected to the opening in one end of the tube 252 while leakage
of air to the outside is substantially eliminated, allowing air
within the driver-unit rear-face air chamber 218 to be securely
flown into the tube 252 (that is, into the acoustic tube 250).
[0073] The tube 252 is a tubular member formed of, for example, a
substance having flexibility. The tube 252 is arranged along the
circumferential direction of the frame 211 having a disk shape, for
example, as shown in FIG. 5. By arranging the tube 252 along the
circumferential direction of the frame 211, it becomes possible to
arrange the tube 252 in a smaller space, and to provide the
acoustic tube 250 without deforming a shape of the housing 240 or
enlarging the housing 240.
[0074] Here, when the inductance component and the resistance
component to a flow of air in the inside of the attachment 251 can
be ignored, a length and an inner cross-sectional area of the tube
252 correspond to a length and an inner cross-sectional area of the
acoustic tube 250. The length and the inner cross-sectional area of
the tube 252 may be optionally set so as to obtain the desired
sound pressure level characteristic in consideration of the sound
pressure level characteristic, for example, as shown in FIG. 3.
More specifically, as described with reference to FIG. 3, the
length and the inner cross-sectional area of the tube 252 can be
optionally set so as to realize a value of such a capacitor Cb and
inductance Mb that the resonance frequency where anti-resonance is
generated is located in the desired frequency band. Note that, when
the inductance component and the resistance component to a flow of
air in the inside of the attachment 251 cannot be ignored, the
length and the inner cross-sectional area of the tube 252 can be
optionally set so that the capacitor Cb and the inductance Mb in a
structure where the attachment 251 is connected to the tube 252 are
the desired value. A detailed method for adjusting the length and
the inner cross-sectional area of the acoustic tube 250 will be
described in detail in <3. Acoustic Characteristic Adjusting
Method> described below.
[0075] In this manner, in the present embodiment, the acoustic tube
250 is formed with a relatively simple configuration of the
attachment 251 and the tube 252. Here, as described with reference
to FIG. 1, the driver unit 210 according to the present embodiment
may have a configuration similar to that of the existing typical
dynamic-type driver unit except for being provided with the
acoustic tube 250. Therefore, in the present embodiment, it is
possible to manufacture the acoustic tube 250 according to the
present embodiment only by forming the ventilation hole 216a in the
frame of the existing typical dynamic-type driver unit, and
mounting the attachment 251 and the tube 252. Therefore, the
improvement in the acoustic characteristic is realized at lower
costs. Note that, in the example shown in FIG. 5, only the one
ventilation hole 216a is provided in the frame 211, but the present
embodiment is not limited thereto. In the present embodiment, a
plurality of ventilation holes 216a may be provided in the frame
211, and the opening of the attachment 251 may be formed so as to
cover the plurality of ventilation holes 216a. When the opening of
the attachment 251 is formed so as to cover the plurality of
ventilation holes 216a, the ventilation between the driver-unit
rear-face air chamber 218 and the acoustic tube 250 will be more
securely performed.
[0076] Referring to FIG. 4 again, the description of the
configuration of the headphone 20 will be continued. The housing
240 accommodates the driver unit 210 therein. The housing 240
corresponds to the housing 140 shown in FIG. 1. On a front face
side of the driver unit 210, formed is a front-face air chamber 225
as a space surrounded by the driver unit 210 and the housing 240.
Further, on a rear face side of the driver unit 210, formed is a
rear-face air chamber 232 as a space surrounded by the driver unit
210 and the housing 240. A volume of the front-face air chamber 225
corresponds to the capacitor C1 in the acoustic equivalent circuit
40.
[0077] The housing 240 may be formed of a plurality of members. In
the example shown in FIG. 4, the housing 240 is formed by joining a
front housing 220 covering the front face side of the driver unit
210 and a rear housing 230 covering the rear face side of the
driver unit 210 together. The front housing 220 and the rear
housing 230 correspond to the front housing 120 and the rear
housing 130 shown in FIG. 1.
[0078] In a partition wall of the front housing 220, provided are
openings 221 and 222 spatially connecting the inside of the housing
240 with the outside. The openings 221 and 222 correspond to the
openings 121 and 122 of FIG. 1. The opening 121 is an opening for
outputting sound to the outside. In a partial region of the front
housing 220, formed is a sound guiding tube 224 as a tubular part
provided so as to project toward the outside, and the opening 221
is provided in a tip end part of the sound guiding tube 224. The
sound guiding tube 224 corresponds to the sound guiding tube 124 of
FIG. 1. In the outer circumference of the tip end part of the sound
guiding tube 224, provided is an earpiece 226 for allowing the
sound guiding tube 124 to be closely fitted to the inner wall of
the external auditory canal of a user. When the user listen to
sound, the tip end part of the sound guiding tube 124 including the
earpiece 226 is inserted into the external auditory canal of the
user. In this manner, in the present embodiment, the headphone 20
may be a so-called canal-type earphone. Further, an equalizer 227
as a ventilation resistance body is provided inside the sound
guiding tube 224. It is possible to adjust sound quality such as
reducing a component in a specific frequency band for sound to be
outputted, by optionally setting a material and a shape of the
equalizer.
[0079] In the opening 222, a ventilation resistance body 223 is
provided so as to block the hole. The ventilation resistance body
223 corresponds to the ventilation resistance body 123 of FIG. 1.
That is, also in the headphone 20, similarly to the headphone 10, a
material and a shape of the ventilation resistance body 223 are
selected so as to substantially block air. In this manner, in the
present embodiment, the front-face air chamber 225 may be a
sealed-type air chamber where it is spatially blocked from the
outside except for the opening 221. A resistance component to a
flow of air of the ventilation resistance body 223 corresponds to
the resistor R1 in the acoustic equivalent circuit 40.
[0080] In a partition wall of the rear housing 230, provided is an
opening 231 spatially connecting the inside of the housing 240 with
the outside. The opening 231 corresponds to the opening 131 of FIG.
1. That is, the opening 231 is formed so as to have such a size
that it can be almost no resistance to a flow of air. In this
manner, in the present embodiment, the rear-face air chamber 232 is
connected to a space outside the housing 240 via the opening 231
while resistance to a flow of air does not almost exist. Therefore,
similarly to the acoustic tube 150 of FIG. 1, the other end of the
acoustic tube 250 according to the present embodiment may be also
provided within the rear-face air chamber 232, or may be provided
outside the housing 240. In any case, it is possible to obtain the
same acoustic characteristic.
[0081] With reference to FIG. 4, the configuration of the headphone
20 according to an embodiment of the present disclosure has been
described above in more detail.
<3. Method for Designing Acoustic Tube and Driver Unit>
[0082] Next, taking the headphone 20 as an example, a specific
method for designing the acoustic tube 250 and the driver unit 210
according to the present embodiment will be described. As described
with reference to FIG. 3, in order to obtain the ideal stepwise
sound pressure level characteristic, it is preferable that the
resonance frequency fh of the anti-resonance generated by the
capacitor Cb and the inductance Mb is included in the frequency
band of 200 (Hz) to 400 (Hz). Here, the inductance Mb depends on
the length and the inner cross-sectional area of the acoustic tube
250, and the capacitor Cb depends on the volume of the driver-unit
rear-face air chamber 218. There will be described below a method
for designing the length and the inner cross-sectional area of the
acoustic tube 250, and the volume of the driver-unit rear-face air
chamber 218 so that the resonance frequency fh of the
anti-resonance is included in the frequency band of 200 (Hz) to 400
(Hz).
[0083] The resonance frequency fh (Hz) of the anti-resonance by the
inductance Mb and the capacitor Cb is expressed by Formula (1)
described below.
[ Math . 1 ] fh = 1 2 .pi. Mb .times. Cb ( 1 ) ##EQU00001##
[0084] Further, when the length of the acoustic tube 250 is L (m)
and the inner cross-sectional area thereof is S (m.sup.2), the
inductance Mb is expressed by Formula (2) described below.
[ Math . 2 ] Mb = .rho. .times. L S ( 2 ) ##EQU00002##
[0085] Here, .rho. (kg/m.sup.3) is air density. Also, when the
volume of the driver-unit rear-face air chamber 218 is V (m.sup.3),
the capacitor Cb is expressed by Formula (3) described below. Note
that c (m/s) is sound velocity.
[ Math . 3 ] Cb = V .rho. c 2 ( 3 ) ##EQU00003##
[0086] It is possible to obtain a condition for the length L and
the inner cross-sectional area S of the acoustic tube 250, and the
volume V of the driver-unit rear-face air chamber 218 so that the
resonance frequency fh of the anti-resonance can be included in the
frequency band of 200 (Hz) to 400 (Hz), by using Formulas (1) to
(3) described above. The results are shown in FIG. 6 and FIG. 7.
FIG. 6 and FIG. 7 are a graphic diagram illustrating a relationship
between the resonance frequency fh of the anti-resonance, and the
length L of the acoustic tube 250, the inner cross-sectional area S
of the acoustic tube 250 and the volume V of the driver-unit
rear-face air chamber 218.
[0087] With reference to FIG. 6, the inner cross-sectional area S
(mm.sup.2) of the acoustic tube 250 is indicated in the horizontal
axis, and the length L (mm) of the acoustic tube 250 is indicated
in the vertical axis, and a relationship between the length L (mm)
and the inner cross-sectional area S (mm.sup.2) for obtaining the
resonance frequency fh=180, 200, 300, 400 and 500 (Hz) is plotted.
Note that, in the graph of FIG. 6, V=180 (mm.sup.3) is fixed. V=180
(mm.sup.3) corresponds to, for example, a case where the diameter
of the frame 211 of the driver unit 210 is 16 (mm).
[0088] In FIG. 6, the range where the resonance frequency fh of the
anti-resonance is included in 200 (Hz) to 400 (Hz) is indicated by
hatching. The result of FIG. 6 shows that the acoustic tube 250
should be designed so that the length L (mm) and the inner
cross-sectional area S (mm.sup.2) of the acoustic tube 250 are
included in the hatching region, in order to be set so that the
resonance frequency fh is included in 200 (Hz) to 400 (Hz) in a
case of V=180 (mm.sup.3). Conversely, when the acoustic tube 250 is
designed so that the length L (mm) and the inner cross-sectional
area S (mm.sup.2) of the acoustic tube 250 are included in the
hatching region, the resonance frequency fh is included in 200 (Hz)
to 400 (Hz), and the stepwise sound pressure level characteristic
can be obtained. For example, when the acoustic tube 250 having the
length L (mm) of 20 (mm) and the inner cross-sectional area S
(mm.sup.2) of 0.20 (mm.sup.2) is configured, it is possible to
generate the anti-resonance having the resonance frequency fh of
around 350 (Hz) to obtain the stepwise sound pressure level
characteristic.
[0089] With reference to FIG. 7, a ratio L/S (1/mm) of the length L
(mm) of the acoustic tube 250 to the inner cross-sectional area S
(mm.sup.2) thereof is indicated in the horizontal axis, and the
volume V (mm.sup.3) of the driver-unit rear-face air chamber 218 is
indicated in the vertical axis, and a relationship between the L/S
(1/mm) and the volume (mm.sup.3) for obtaining the resonance
frequency fh=180, 200, 300, 400 and 500 (Hz) is plotted. In FIG. 7,
similarly to FIG. 6, the range where the resonance frequency fh of
the anti-resonance is included in 200 (Hz) to 400 (Hz) is indicated
by hatching. The result of FIG. 7 shows that the acoustic tube 250
and the driver unit 210 should be designed so that the ratio L/S
(1/mm) of the length L (mm) of the acoustic tube 250 to the inner
cross-sectional area S (mm.sup.2), and the volume V (mm.sup.3) of
the driver-unit rear-face air chamber 218 are included in the
hatching region, in order to be set so that the resonance frequency
fh is included in 200 (Hz) to 400 (Hz). Conversely, when the
acoustic tube 250 and the driver unit 210 are designed so that the
ratio L/S (1/mm) of the length L (mm) of the acoustic tube 250 to
the inner cross-sectional area S (mm.sup.2), and the volume V
(mm.sup.3) of the driver-unit rear-face air chamber 218 are
included in the hatching region, the resonance frequency fh is
included in 200 (Hz) to 400 (Hz), and the stepwise sound pressure
level characteristic can be obtained. For example, when the
acoustic tube 250 having the volume V (mm.sup.3) of 180 (mm.sup.3),
and the ratio L/S (1/mm) of the length L (mm) of the acoustic tube
250 to the inner cross-sectional area S (mm.sup.2) of 102 (1/mm) is
configured, it is possible to generate the anti-resonance having
the resonance frequency fh of around 350 (Hz) to obtain the
stepwise sound pressure level characteristic.
[0090] As described above, in the present embodiment, it is
possible to design the structure of the acoustic tube 250 and the
driver unit 210 in the headphone 20 by using Formulas (1) to (3)
described above. Here, the design of the acoustic tube 250 and the
driver unit 210 will be described more specifically by using
numerical values.
[0091] A value of the volume V (mm.sup.3) of the driver-unit
rear-face air chamber 218 is almost determined by the diameter of
the frame 211 of the driver unit 210. Here, the size of the driver
unit 210, that is, the diameter of the frame 211 can be limited to
some specific values by standards. For example, in a relatively
small headphone such as a canal-type earphone, the driver unit 210
having a relatively small size is preferably applied. Here, as an
example of the driver unit 210 assumed to be preferably applied in
the canal-type earphone, a case of the frame 211 of the driver unit
210 having the diameter of 9 (mm) or 16 (mm) will be
considered.
[0092] For the driver unit 210 having these standards, the
relationship between the resonance frequency fh of the
anti-resonance, and the length L and the inner cross-sectional area
S of the acoustic tube 250 was calculated specifically by using
Formulas (1) to (3) described above. The calculation results are
shown in the table described below. When the diameter of the frame
211 is 9 (mm), the volume V (mm.sup.3) of the driver-unit rear-face
air chamber 218 can be considered to be around 50 (mm.sup.3).
Further, when the diameter of the frame 211 is 16 (mm), the volume
V (mm.sup.3) of the driver-unit rear-face air chamber 218 can be
considered to be around 180 (mm.sup.3). Accordingly, in the
calculation for obtaining the table below, as a value of the volume
V (mm.sup.3) of the driver-unit rear-face air chamber 218, 50
(mm.sup.3) and 180 (mm.sup.3) were used.
TABLE-US-00001 TABLE 1 L/S(1/mm.sup.2) Diameter (mm) Diameter
16(mm) Resonance frequency fh(Hz) (V = 50(mm.sup.3)) (V =
180(mm.sup.3)) 150 1999 540 180 1389 374 200 1124 303 300 500 135
350 377 101 400 281 76 500 179 48 600 125 35
[0093] With reference to the table above, it turns out that the
ratio L/S (1/mm) of the length L (mm) to the inner cross-sectional
area S (mm.sup.2) in the acoustic tube 250 should be 76 to 1124
(1/mm) in order to be set so that the resonance frequency fh is
included in 200 (Hz) to 400 (Hz). Further, when the volume V
(mm.sup.3) of the driver-unit rear-face air chamber 218 is 50
(mm.sup.3), it turns out that the ratio L/S (1/mm) should be 281 to
1124 (1/mm) in order to be set so that the resonance frequency fh
is included in 200 (Hz) to 400 (Hz). Further, when the volume V
(mm.sup.3) of the driver-unit rear-face air chamber 218 is 180
(mm.sup.3), it turns out that the ratio L/S (1/mm) should be 76 to
303 (1/mm) in order to be set so that the resonance frequency fh is
included in 200 (Hz) to 400 (Hz).
[0094] As described above, in the present embodiment, the shape
(the length and the inner cross-sectional area) of the acoustic
tube 250 and the shape of the driver unit 210 can be designed so
that the resonance frequency fh is included in the desired
frequency band, for example, 200 (Hz) to 400 (Hz), by using
Formulas (1) to (3) described above. In the example described
above, as an example of the method for designing the acoustic tube
250 and the driver unit 210 according to the present embodiment,
the method for designing the acoustic tube 250 and the driver unit
210 has been described on the condition that the resonance
frequency fh is included in 200 (Hz) to 400 (Hz), and the volume V
(mm.sup.3) of the driver-unit rear-face air chamber 218 is 50
(mm.sup.3) or 180 (mm.sup.3), but the present embodiment is not
limited thereto. Also on the condition that the resonance frequency
fh is included in another frequency band, or on the condition that
the volume V (mm.sup.3) of the driver-unit rear-face air chamber
218 has another value, it is possible to design the acoustic tube
250 and the driver unit 210 by using the same method described
above.
[0095] Note that, when a value of the length L (mm) and the inner
cross-sectional area S (mm.sup.2) of the acoustic tube 250 is
designed, machining accuracy in manufacturing the acoustic tube 250
may be considered. For example, a minimum value of the length L
(mm) and the inner cross-sectional area S (mm.sup.2) may be limited
to such a value that the acoustic tube 250 can be manufactured
within a predetermined dimensional tolerance. Further, when
designing the driver unit 210, a shape of the housing 240
accommodating the driver unit 210 and an acoustic characteristic of
sound generated by the driver unit 210 can be considered. When the
canal-type earphone exemplified in FIG. 4 is used, a size of the
housing 240 is relatively small, and for example when a so-called
overhead-type headphone is used, a size of the housing 240 is
larger. Further, a shape of the housing can be set also in
consideration of wearability and designability of the headphone 20
by a user. Further, a shape of the driver unit 210 can directly
affect an acoustic characteristic of sound generated by the driver
unit 210. Therefore, in design of a shape of the driver unit 210, a
shape of the housing 240, an acoustic characteristic of the driver
unit 210 and the like may be comprehensively considered.
[0096] Here, for example, as described in Patent Literature 1 and
Patent Literature 2, an acoustic characteristic of the existing
headphone will be considered. For example, in the headphone
described in Patent Literature 1, a configuration corresponding to
the acoustic tube 250 is not provided. Therefore, the acoustic
equivalent circuit of the headphone described in Patent Literature
1 corresponds to one where the inductance Mb and the resistor Rb2
do not exist in the acoustic equivalent circuit 40 of FIG. 2.
Therefore, the anti-resonance by the capacitor Cb and the
inductance Mb cannot bet generated, so that the dip of the sound
pressure level is not formed. In this manner, since a configuration
corresponding to the acoustic tube 250 is not provided in the
existing headphone, only a value of the resistor Rb1 exists as a
parameter for adjusting the sound pressure level, making it
difficult to obtain the stepwise sound pressure level
characteristic. On the other hand, in the present embodiment, the
dip of the sound pressure level due to the anti-resonance can be
formed in the predetermined frequency by providing the acoustic
tube 250. Since the dip can form a stepwise shape in the stepwise
sound pressure level characteristic, for example, the stepwise
sound pressure level characteristic described above can be
realized. In this manner, in the present embodiment, since a
parameter for adjusting the sound pressure level characteristic is
increased, it becomes possible to easily realize the desired sound
pressure level characteristic to further improve the acoustic
characteristics.
[0097] Furthermore, for example, in the headphone described in
Patent Literature 2 described above, the duct structure similar to
the acoustic tube 250 according to the present embodiment is
provided. Therefore, in the existing headphone, the anti-resonance
due to the capacitor Cb in the driver-unit rear-face air chamber
and the inductance Mb in the duct structure can be generated. The
investors created the acoustic equivalent circuit for the headphone
described in Patent Literature 2 described above, and similarly to
the above description, calculated a relationship between the
resonance frequency fh of the anti-resonance, and the length L and
the inner cross-sectional area S in the duct structure and the
volume V of the driver-unit rear-face air chamber. As a result, in
the headphone described in Patent Literature 2 described above, it
turns out that the L/S (1/mm) of the tubular duct structure is
around 11 (1/mm), and the resonance frequency fh is around 500
(Hz). In order to obtain the sound pressure level characteristic
where the sound pressure level is reduced in a stepwise manner from
the low range to the middle range, as described above, it is
preferable that the resonance frequency fh is included in 200 (Hz)
and 400 (Hz), but it can be said that the resonance frequency fh in
the existing headphone described in Patent Literature 2 described
above is not included in this range.
[0098] Here, in the headphone described in Patent Literature 2
described above, the tubular duct structure is formed in one part
of the housing. Therefore, in order to change the length L and the
inner cross-sectional area S of the tube, it is necessary to change
a shape of the housing, so that the resonance frequency fh cannot
be easily adjusted. In this manner, in the headphone described in
Patent Literature 2 described above, it is difficult to adjust the
value, for example, so that the resonance frequency fh is included
in 200 (Hz) to 400 (Hz). On the other hand, in the present
embodiment, the acoustic tube 250 is configured by the relatively
simple configuration, for example, as shown in FIG. 5 and FIG. 11
to be described later. Further, the acoustic tube 250, for example,
as shown in FIG. 5, can adjust the resonance frequency fh more
easily by changing the length and the inner cross-sectional area of
the tube 252. In this manner, in the present embodiment, it is
possible to adjust the sound pressure level characteristic by the
more simple method, so that, for example, the stepwise sound
pressure level characteristic as described above can be realized
more easily.
[0099] Furthermore, in the headphone described in Patent Literature
2 described above, similarly to the present embodiment, the housing
is formed by joining the front housing covering the front face side
of the driver unit, and the rear housing covering the rear face
side of the driver unit together. The tubular duct structure is
formed in the partial region of the rear housing, and spatially
connects the rear-face air chamber with the outside of the housing.
Therefore, for example, when the volume of the rear-face air
chamber changes for the reasons that a gap is generated in the
junction part between the front housing and the rear housing, or
the like, since the relationship between the capacitance component
of the rear-face air chamber, and the resistance component and the
inductance component of the tubular duct structure changes, the
tubular duct structure may not exhibit the desired performance. In
this manner, in the headphone described in Patent Literature 2
described above, in order to realize the desired acoustic
characteristic, the high airtightness of the rear-face air chamber
is required. On the other hand, in the present embodiment, on end
of the acoustic tube 250 is directly connected to the frame 211 of
the driver unit 210, and the acoustic tube 250 spatially connects
the driver-unit rear-face air chamber 218 with the rear-face air
chamber 232 as the outside of the driver unit 210. Further, the
rear-face air chamber 232 is spatially connected to the outside of
the housing 240 via the opening 231 while there is almost no
resistance. Therefore, in the present embodiment, for example, even
when a gap is generated in the junction part between the front
housing 220 and the rear housing 230 to reduce the airtightness of
the rear-face air chamber 232, the performance of the acoustic tube
250 does not change and the desired sound pressure level
characteristic can be realized. Further, since the frame 211 of the
driver unit 210 can be integrally molded as a plate-like member,
the driver-unit rear-face air chamber 218 hardly causes a reduction
in airtightness due to assembly of the members. In this manner, in
the present embodiment, it becomes possible to improve the acoustic
characteristic more stably.
<4. Modification>
[0100] Next, with reference to FIG. 8A to FIG. 12B, a modification
of the headphone according to an embodiment of the present
disclosure will be described. The headphone according to the
present modification is a so-called multi-way headphone on which a
plurality of driver units are mounted.
[0101] Here, the headphone according to the present modification is
a canal-type earphone where an acoustic tube projected in a partial
region of a housing is inserted into the external auditory canal of
a user. Further, the headphone according to the present
modification is inserted into the external auditory canal so that
the rear face side faces a rear side of the user, and the front
face side faces a front side of the user. In the description of the
present modification below, the horizontal direction and the
vertical direction when viewed from the user while the headphone
according to the present modification is inserted into the external
auditory canal of the user, are referred to as an x-axis direction
and a y-axis direction, respectively.
[0102] With reference to FIG. 8A to FIG. 10B, a configuration of
the headphone according to a modification of an embodiment of the
present disclosure will be described. FIG. 8A to FIG. 8D are an
appearance diagram illustrating a configuration of the headphone
according to a modification of an embodiment of the present
disclosure. FIG. 8A is an appearance diagram illustrating a state
of the headphone according to the present modification when it is
viewed from the front face side (that is, a positive direction of
the z axis). FIG. 8B is an appearance diagram illustrating a state
of the headphone according to the present modification when it is
viewed from the rear face side (that is, a negative direction of
the z axis). FIG. 8C is an appearance diagram illustrating a state
of the headphone according to the present modification when it is
viewed from the y-axis direction. FIG. 8D is an appearance diagram
illustrating a state of the headphone according to the present
modification when it is viewed from the x-axis direction.
[0103] Furthermore, FIG. 9A to FIG. 9C are a diagram virtually
transparently illustrating a part of the housing and illustrating a
state of structural members within the housing, in the headphone of
FIG. 8A to FIG. 8C. FIG. 9A transparently illustrates a part of the
housing facing the positive direction of the z-axis (a front
housing 320 to be described later) in the headphone of FIG. 8A.
FIG. 9B transparently illustrates a part of the housing facing the
negative direction of the z-axis (a rear housing 330 to be
described later) in the headphone of FIG. 8B. FIG. 9C transparently
illustrates a part of the housing facing the positive direction and
the positive direction of the z-axis (the front housing 320 and the
rear housing 330) in the headphone of FIG. 8C. Note that, in FIG.
9A to FIG. 9C, the structural members within the housing that can
be observed passing through the front housing 320 and/or the rear
housing 330 are indicated by the thick line, and the other members
are indicated by the thin line.
[0104] Furthermore, FIG. 10A and FIG. 10B are a cross-sectional
diagram of the headphone of FIG. 8A. FIG. 10A is a cross-sectional
diagram illustrating a state in the A-A cross section of the
headphone of FIG. 8A. FIG. 10B is a cross-sectional diagram
illustrating a state in the B-B cross section of the headphone of
FIG. 8A.
[0105] With reference to FIG. 8A to FIG. 10B, the headphone 30
according to the present embodiment includes a dynamic-type driver
unit 310, a BA-type driver unit 370, and a housing 340
accommodating the dynamic-type driver unit 310 and the BA-type
driver unit 370 therein. Note that the structural members
illustrated in FIG. 8A to FIG. 10B are simplified for the
description of the present embodiment, and the headphone 30 may
further include structural members not shown. Since a function
configuration not shown can be already known as a configuration in
the existing typical headphone, the detailed description is
omitted.
[0106] Here, the headphone 30 according to the present modification
corresponds to one where the BA-type driver unit 370 is further
mounted on the headphone 20 of FIG. 4. Therefore, also in the
headphone 30 according to the present modification, a part of the
structural members corresponds to the configuration of the
headphone 10 described with reference to FIG. 1. In the description
of each structural member of the headphone 30, a correspondence
relationship with each structural member of the headphone 10 of
FIG. 1 will be described. Further, since the corresponding
structural members have functions similar to each other, the
detailed descriptions for ones corresponding to the structural
members already described with reference to FIG. 1 in the
structural members of the headphone 30 are omitted. Further, the
acoustic equivalent circuit of the headphone 30 can be one where
elements corresponding to the structural members newly added in the
present modification are added to the acoustic equivalent circuit
40 of FIG. 2. Therefore, similarly to FIG. 1, symbols of the
elements in the acoustic equivalent circuit 40 are added to signs
with which the structural members of the headphone 30 are partially
denoted.
[0107] The dynamic-type driver unit 310 has a frame 311, a
diaphragm 312, a magnet 313, a plate 314, and a voice coil 315. The
dynamic-type driver unit 310 corresponds to the driver unit 110 of
FIG. 1. Further, the frame 311, the diaphragm 312, the magnet 313,
the plate 314, and the voice coil 315 correspond to the frame 111,
the diaphragm 112, the magnet 113, the plate 114, and the voice
coil 115 of FIG. 1. A driver-unit rear-face air chamber 318 is
formed between the frame 311 and the diaphragm 312. An element
corresponding to electromotive force when the diaphragm 312 is
vibrated corresponds to the signal source (electromotive force) Vs
in the acoustic equivalent circuit 40. Further, mass, mechanical
resistance and compliance in the dynamic-type driver unit 310
corresponds to the inductance Mo, the resistance Ro and the
capacitor Co in the acoustic equivalent circuit 40, respectively.
Further, the volume of the driver-unit rear-face air chamber 318
corresponds to the capacitor Cb in the acoustic equivalent circuit
40.
[0108] In the frame 311 of the dynamic-type driver unit 310,
provided are ventilation holes 316a and 316b penetrating the frame
311 in the z-axis direction. The ventilation holes 316a and 316b
correspond to the ventilation holes 116a and 116b shown in FIG. 1.
The ventilation hole 316a is formed at a position radially shifted
from the center of the frame 311 by a predetermined distance, and
spatially connects the edge part of the driver-unit rear-face air
chamber 318 with the outside of the dynamic-type driver unit 310.
Further, the ventilation hole 316b is formed at the substantial
center of the frame 311, and spatially connects the dome part of
the driver-unit rear-face air chamber 318 with the outside of the
dynamic-type driver unit 310.
[0109] In the ventilation hole 316b, a ventilation resistance body
317a is provided so as to block the hole. The ventilation
resistance body 317a corresponds to the ventilation resistance body
117b of FIG. 1. A resistance component to a flow of air, of the
ventilation resistance body 317a corresponds to the resistor Rb1 in
the acoustic equivalent circuit 40.
[0110] Here, a material and a shape of the ventilation resistance
body 317a may be optionally set so as to obtain the desired sound
pressure level characteristic, for example, in consideration of the
sound pressure level characteristic as shown in FIG. 3. More
specifically, as described with reference to FIG. 3, a material and
a shape of the ventilation resistance body 317a can be optionally
set so that a value of the resistor Rb1 for obtaining the stepwise
sound pressure level characteristic can be realized.
[0111] To the ventilation hole 316a, one end of the acoustic tube
350 is connected. Here, with reference to FIG. 11, a configuration
of the acoustic tube 350 in the headphone 30 will be described in
more detail. FIG. 11 is an explanatory diagram for explaining a
structure of the acoustic tube 350 according to the present
modification. In FIG. 11, for convenience, only the frame 311 of
the structural members of the dynamic-type driver unit 310 is
shown, and a state where a rod-like member to be described later is
removed from the frame 311, and a state where the acoustic tube 350
is formed by attaching the rod-like member 351 to the frame 311 are
shown.
[0112] With reference to FIG. 11, the acoustic tube 350 is
configured by the rod-like member 351. A groove 352 is formed in
one face of the rod-like member 351 in a longitudinal direction.
Further, at least one end of the groove 352 is formed so as to
reach an end of the rod-like member 351. The acoustic tube 350 is
formed by arranging the rod-like member 351 so that a face on which
the groove 352 of the rod-like member 351 is formed is closely
fitted to one face on a rear face side of the frame 311, and at
least one part of the groove 352 is in contact with the ventilation
hole 361a. When the rod-like member 351 is arranged in this manner,
the acoustic tube 350 having a tubular structure is realized by one
face of the frame 311 and the groove 352. Air flown into the groove
352 via the ventilation hole 316a from the driver-unit rear-face
air chamber 318 is flown out to the outside of the dynamic-type
driver unit 310 through the tubular structure configured by one
face of the frame 311 and the groove 352.
[0113] Here, the acoustic tube 350 is a member corresponding to the
acoustic tube 150 of FIG. 1. The acoustic tube 350 spatially
connects the driver-unit rear-face air chamber 318 with the outside
of the dynamic-type driver unit 310 via the tube. As shown in FIG.
11, in the present modification, the tubular part of the acoustic
tube 359 is configured by the groove 352 of the rod-like member
351. Therefore, it can be said that an inductance component and a
resistance component to a flow of air in the acoustic tube 350
correspond to an inductance component and a resistance component to
a flow of air in the groove 352 of the rod-like member 351. The
inductance component and the resistance component correspond to the
inductance Mb and the resistor Rb in the acoustic equivalent
circuit 40, respectively.
[0114] Note that a part of the rod-like member 351 in contact with
the ventilation hole 361a may be a part corresponding to one end of
the groove 352, and a projection engaged with the ventilation hole
361a may be provided in one end of the groove 351. Providing the
projection makes it easy to mount the rod-like member 351 to the
frame 311 and allows the rod-like member 351 to be securely mounted
to the frame 311. However, a size of the projection is set to such
a size that the ventilation hole 316a is not totally blocked,
preventing a flow of air from the driver-unit rear-face air chamber
318 to the groove 352 from being disturbed. Further, contact faces
between the rod-like member 351 and the frame 311 may be bonded,
for example, by various types of adhesives, a double-sided tape, or
the like. When the contact faces between the rod-like member 351
and the frame 311 are bonded, for example, by an adhesives, or the
like, the ventilation hole 316a is spatially connected to the
groove 352 while leakage of air to the outside from a part other
than the groove 352 is almost eliminated, so that air within the
driver-unit rear-face air chamber 318 is securely flown into the
groove 352 (that is, into the acoustic tube 350).
[0115] Furthermore, the rod-like member 351 may be curved so as to
have the curvature substantially equal to or equal to or less than
the circumference of the substantial disk-like frame 311. When the
rod-like member 351 is curved so as to have the curvature
substantially equal to or equal to or less than the circumference
of the substantial disk-like frame 311, the rod-like member 351
will be arranged along the circumference direction of the frame 311
to allow the rod-like member 351 to be arranged in a smaller space,
allowing the acoustic tube 350 to be provided without deforming a
shape of the housing 340 or enlarging the housing 340.
[0116] Here, a length and an inner cross-sectional area of the
groove 352 formed in the rod-like member 351 correspond to a length
and an inner cross-sectional area of the acoustic tube 350. The
length and the inner cross-sectional area of the groove 352 may be
optionally set so as to obtain the desired sound pressure level
characteristic, for example, in consideration of the sound pressure
level characteristic shown in FIG. 3. More specifically, as
described with reference to FIG. 3, the length and the inner
cross-sectional area of the groove 352 can be optionally set so as
to realize a value of such a capacitor Cb and inductance Mb that
the resonance frequency generating the anti-resonance is located in
the desired frequency band. Specifically, the length and the inner
diameter of the groove 352 may be optionally set by the method
described in <3. Method for Designing Acoustic Tube and Driver
Unit> described above.
[0117] In this manner, in the present embodiment, the acoustic tube
350 is formed by a relatively simple configuration of the rod-like
member 351. Here, as described with reference to FIG. 1, the
dynamic-type driver unit 310 according to the present embodiment
may have a configuration similar to that of the existing typical
dynamic-type driver unit except for being provided with the
acoustic tube 350. Therefore, in the present embodiment, it is
possible to manufacture the acoustic tube 350 according to the
present embodiment only by forming the ventilation hole 361a in the
frame of the existing typical dynamic-type driver unit and mounting
the rod-like member 351 thereon. Therefore, the improvement in the
sound characteristic is realized at lower costs. Note that, in the
example shown in FIG. 11, only the one ventilation hole 316a is
provided in the frame 311, but the present modification is not
limited thereto. In the present modification, a plurality of
ventilation holes 316a may be provided along the groove 352. When
the plurality of ventilation holes 316a are provided, the
ventilation holes 316a will be more securely in contact with the
groove 351, and even when a positional shift between the
ventilation holes 361a and the groove 352 or the like occurs, the
ventilation holes 316a will be more securely in contact with the
groove 351, preventing the ventilation from being insufficient.
[0118] Furthermore, the acoustic tube 350 according to the present
modification is configured by the rod-like member 351, but the
present modification is not limited thereto. In the present
modification, the acoustic tube 350, similarly to the acoustic tube
250 of FIG. 5, may be configured by the attachment 251 and the tube
252. Further, conversely, the acoustic tube 350 configured by the
rod-like member 351, similar to the acoustic tube 350 of FIG. 11,
may be applied to the headphone 20 of FIG. 4. In this manner, in
the present embodiment, the acoustic tube may be a tubular member
having a predetermined length and inner cross-sectional area, and
the specific configuration may be optionally set in consideration
with costs of the procurement of members configuring the acoustic
tube, the assembly of the members to the driver unit, and the like.
Further, the acoustic tube according to the present embodiment may
be formed integrally with the frame of the driver unit, for
example.
[0119] Referring to FIG. 8A to FIG. 10B again, the description of
the configuration of the headphone 30 will be continued. The
housing 340 accommodates the dynamic-type driver unit 310 and the
BA-type driver unit 370 therein. The housing 340 corresponds to the
housing 140 of FIG. 1.
[0120] The housing may be configured by a plurality of members. In
the example shown in FIG. 8A to FIG. 10B, unlike the headphone 10
of FIG. 1, the housing 340 is configured by four members. That is,
the housing 340 includes the front housing 320 covering a front
face side of the dynamic-type driver unit 310, the rear housing 330
covering a rear face side of the dynamic-type driver unit 310, a
middle housing 360 located between the front housing 320 and the
rear housing 330 and connecting between both, and a cable housing
390 covering a cable 391 supplying an audit signal to the
dynamic-type driver unit 310 and the BA-type driver unit 370. In
this manner, in the present modification, the front housing 320 is
not directly connected to the rear housing 330, and the middle
housing 360 is provided between both.
[0121] In a partition wall of the middle housing 360, provided is
an opening 361 spatially connecting the inside of the housing 340
with the outside. The opening 361 corresponds to the opening 121 of
FIG. 1, and is an opening for outputting sound to the outside. In a
partial region of the middle housing 360, formed is a sound guiding
tube 364 as a tubular part provided so as to project toward the
outside, and the opening 361 is provided in a tip end part of the
sound guiding tube 364. The sound guiding tube 361 corresponds to
the sound guiding tube 124 of FIG. 1. In the outer circumference of
the tip end part of the sound guiding tube 364, an earpiece (not
shown except for FIG. 12B) is provided. When a user listen to
sound, the tip end part of the sound guiding tube 364 including the
earpiece is inserted into the external auditory canal of the user.
Further, an equalizer 367 as a ventilation resistance body is
provided inside the sound guiding tube 364. Since the equalizer 367
has a function similar to that of the equalizer 227 of FIG. 4, the
detailed description is omitted.
[0122] In the present modification, a space within the housing 340
is divided into a dynamic-type driver-unit accommodation chamber
326 as a space accommodating the dynamic-type driver unit 310, and
a BA-type driver-unit accommodation chamber 327 as a space
accommodating the BA-type driver unit 370, by a partition wall 362
that can be formed integrally with the middle housing 360. As shown
in FIG. 10A and FIG. 10B, the dynamic-type driver-unit
accommodation chamber 326 is a space surrounded by the rear housing
330 and the partition wall 362, and the BA-type driver-unit
accommodation chamber 326 is a space surrounded by the front
housing 320 and the partition wall 362. Note that, in the present
modification, the partition wall 362 may not be formed integrally
with the middle housing 360, and may be arranged within the housing
340 as another member.
[0123] The dynamic-type driver-unit accommodation chamber 326 is
further divided into a front-face air chamber 325 as a space on a
side being provided with a diaphragm 312, and a rear-face air
chamber 332 as a space on a side opposite to the side, by the frame
311 of the dynamic-type driver unit 310. As shown in FIG. 10A and
FIG. 10B, the front-face chamber 325 is a space surrounded by the
partition wall 362 and the frame 311, and the rear-face air chamber
332 is a space surrounded by the rear housing 330 and the frame
311. A volume of the front-face air chamber 325 corresponds to the
capacitor C1 in the acoustic equivalent circuit 40.
[0124] In the BA-type driver-unit accommodation chamber 327, the
two BA-type driver units 370 are accommodated. In the example shown
in FIG. 9A, FIG. 10A and FIG. 10B, the two BA-type driver units 370
are arranged in the BA-type driver unit 327 while being
accommodated within a driver-unit housing 371. The driver-unit
housing 371 is a support member for fixing the BA-type driver unit
370 to a predetermined position, and has a function for defining a
flow path around the BA-type driver unit 370 and controlling a flow
of air. For example, a predetermined space around the BA-type
driver unit 370 is sealed by the driver-unit housing 371, and a
space on a front face side of the BA-type driver unit 370 is
connected to a space provided with the sound guiding tube 364 by
the flow path optionally provided within the driver-unit housing
371. In this manner, sound discharged from the BA-type driver unit
370 can be guided to a direction where the sound guiding tube 364
is provided, by the driver-unit housing 371.
[0125] In the partition wall 362, ventilation holes 333, 368 and
369 are provided. The ventilation hole 333 is provided at such a
position as to spatially connect the rear-face air chamber 332 with
the BA-type driver-unit accommodation chamber 327. Further, the
ventilation hole 333 is formed so as to have such a size that it
can be almost no resistance to a flow of air. In this manner, in
the present modification, the BA-type driver-unit accommodation
chamber 327 can be considered to be a part of the rear-face chamber
332.
[0126] In the partition wall 362, the ventilation hole 368 is
formed at such a position as to spatially connect a space provided
with the sound guiding tube 364 with the front-face air chamber
325. In this manner, the space provided with the sound guiding tube
364 can be said to be a part of the front-face air chamber 325.
Sound discharged from the dynamic-type driver unit 310 reaches the
sound guiding tube 364 via the ventilation hole 368 and is
outputted to the outside. In this manner, in the headphone 30, the
sound generated from the dynamic-type driver unit 310 is combined
with the sound generated from the BA-type driver unit 370 in the
space provided with the sound guiding tube 364, and is finally
outputted to the outside from the opening 361. Further, a size of
the ventilation hole 368 can be set in consideration with the
acoustic characteristic of the sound generated from the
dynamic-type driver unit 310. For example, it becomes possible to
control the acoustic characteristic in the high range in the
dynamic-type driver unit 310 by adjusting the size of the
ventilation hole 368.
[0127] In the partition wall 362, the ventilation hole 369 is
formed at such a position as to spatially connect the front-face
air chamber 325 with the BA-type driver unit 370. Further, in the
ventilation hole 369, a ventilation resistance body 363 is provided
so as to block the ventilation hole 369. The ventilation resistance
body 363 is formed of, for example, a material similar to that of a
ventilation resistance body 317a, and acts as a resistance
component to a flow of air. A resistance component to a flow of air
between the front-face air chamber 325 and the BA-type driver-unit
accommodation chamber 327 can be adjusted by a size of the
ventilation hole 369, and a material and a shape of the ventilation
resistance body 363. As described above, the BA-type driver-unit
accommodation chamber 327 can be considered to be a part of the
rear-face air chamber 332. Further, as described later, the
rear-face air chamber 332 can be spatially connected to the outside
of the housing 340 via the opening 331. Therefore, the adjustment
of the resistance component to a flow of air between the front-face
air chamber 325 and the BA-type driver-unit accommodation chamber
327 corresponds to the adjustment of a sealing degree of the
front-face air chamber 325. The acoustic characteristic of the
sound outputted from the opening 361 can be adjusted by adjusting
the sealing degree. Therefore, the size of the ventilation hole
369, and the material and the shape of the ventilation resistance
body 363 can be set in consideration of the acoustic characteristic
of sound discharged from the dynamic-type driver unit 310 and the
BA-type driver unit 370.
[0128] Here, the dynamic-type driver unit 310 and the BA-type
driver unit 370 can be designed so as to output sound having
different sound pressure level characteristics, respectively. For
example, the dynamic-type driver unit 310 can be designed so that
the sound pressure level in the low range and the high range is
relatively large, and the BA-type driver unit 370 can be designed
so that the sound pressure level in the middle range is relatively
large. Further, the two BA-type driver units 370 may be designed so
as to have the sound pressure level characteristics different from
each other. The dynamic-type driver unit 310 and the BA-type driver
units 370 are designed so as to mutually complement the sound
pressure level when the sound outputted from the dynamic-type
driver unit 310 is combined with the sound outputted from the two
BA-type driver units 370, thereby realizing the excellent acoustic
characteristic over the wide frequency band.
[0129] Note that, in the present modification, it is possible to
apply a typical BA-type driver unit 370 as the BA-type driver unit
370. Therefore, the detailed description of a function and a
configuration of the BA-type driver unit 370 is omitted. Further,
the number of the BA-type driver units 370 mounted is not limited
to the example shown in FIG. 8A to FIG. 10B. The number, the
acoustic characteristic and the like of the BA-type driver unit 370
mounted may be optionally set in consideration of the acoustic
characteristic of the dynamic-type driver unit 310 and the acoustic
characteristic of the sound finally outputted.
[0130] Note that, in the example shown in FIG. 8A to FIG. 10B, when
the resistance component of the ventilation resistance body 363 is
sufficiently large, it can be considered that the opening spatially
connecting the front-face air chamber 325 with the outside is not
provided in the front-face air chamber 325 except for the opening
361. In this manner, the headphone 30 according to the present
modification can be said to be a sealed-type headphone. The present
modification is not limited thereto, however, in the front housing
320 and/or the middle housing 360, such another opening as to
spatially connect the front-face air chamber 325 with the outside,
corresponding to the opening 122 of FIG. 1, may be further provided
in addition to the ventilation hole 369. When another opening is
provided, however, a ventilation resistance body for almost
blocking a flow of air can be arranged in the opening in order to
allow the headphone 30 to be the sealed-type headphone.
[0131] In a partition wall of the rear housing 330, provided is an
opening 331 spatially connecting the inside of the housing 340 with
the outside. The opening 331 corresponds to the opening 131 of FIG.
1. That is, the opening 331 is formed so as to have such a size
that it can be almost no resistance to a flow of air. In this
manner, in the present modification, the rear-face air chamber 332
is connected to a space outside the housing 340 via the opening 331
while resistance to a flow of air does not almost exist. Therefore,
similarly to the acoustic tubes 150 and 250, the other end of the
acoustic tube 350 according to the present modification may be also
provided within the rear-face air chamber 332, or may be provided
outside the housing 340. In any case, it is possible to obtain the
same acoustic characteristic.
[0132] The cable housing 390 accommodates the cable 391 for
transmitting an audio signal therein. A shape of the cable housing
390 can be set according to a pull-out direction of the cable
391.
[0133] Here, with reference to FIG. 12A and FIG. 12B, a wearing
example of the headphone 30 according to the present modification
will be described. FIG. 12A and FIG. 12B are a schematic diagram
illustrating a state of the headphone 30 according to the present
modification, being worn on a user. FIG. 12B illustrates a state in
the C-C cross section of FIG. 12A.
[0134] With reference to FIG. 12A and FIG. 12B, when the sound
guiding tube 364 of the headphone 30 is inserted into the external
auditory canal of a user, the cable 391 is pulled out upward and
diagonally forward when viewed from the user. The cable 391 is then
suspended from the back of the auricle of the user so as to
surround the auricle from the front to the back, and is connected
with an acoustic apparatus outputting an audio signal. The cable
391 is pulled out to the direction shown in FIG. 12A and FIG. 12B,
and is pulled out so as to surround the auricle of the user, to
thereby improve the wearability when the user wears the headphone
30. However, the pull-out direction of the cable 391 is not limited
thereto, and is optionally set in consideration of the wearability
to the user.
[0135] Furthermore, as shown in FIG. 12A and FIG. 12B, the
headphone 30 is inserted into the external auditory canal so that
the rear face side faces the rear side of the user, and the front
face side faces the front side of the user. As shown in FIG. 9A to
FIG. 9C, FIG. 10A and FIG. 10B, in the headphone 30, the
dynamic-type driver unit 310 is arranged on the rear face side, and
the BA-type driver units 370 are arranged on the front face side.
In this manner, the headphone 30 is worn so that the dynamic-type
driver unit 310 is located on the back side of the user, and the
BA-type driver units 370 are located on the front side of the
user.
[0136] Here, for example, when the dynamic-type driver unit 310 is
designed so that the sound pressure level in the low range is
relatively large, and the BA-type driver units 370 are designed so
that the sound pressure level in the higher range than that is
relatively large, it is preferable that the BA-type driver units
370 are arranged at a position closer to the sound guiding tube 364
in order to secure the predetermined sound pressure level for the
output of the BA-type driver units 370. Therefore, when the BA-type
driver units 370 are arranged on the rear face side (that is, the
back side of the user), it is necessary that the sound guiding tube
364 is also made projected from a region on a more back side of the
housing 340. When the sound guiding tube 364 is provided on the
back side, since such a configuration that it is provided on a
relatively front side of the sound guiding tube 364 is often used,
the housing 340 can have a shape swollen to the front side. When
the housing 340 has a shape swollen to the front side, the housing
may come into contact with the tragus when being worn, preventing
the comfortable wearability. In the present modification, when the
dynamic-type driver unit 310 is arranged on the rear face side, and
the BA-type driver units 370 are arranged on the front face side,
since the sound guiding tube 364 can be provided on a relatively
front side, the predetermined sound pressure level for the output
of the BA-type driver units 370 is secured and the comfortable
wearability is realized.
[0137] With reference to FIG. 8A to FIG. 10B, the configuration of
the headphone 30 according to a modification of an embodiment of
the present disclosure has been described above in detail. Here,
also in the headphone 30, similarly to the headphone 10 and the
headphone 20 described above, it is possible to analyze the
acoustic characteristic by using the sound equivalent circuit.
However, in the headphone 30, the BA-type driver units 370 are
added to the headphone 10 and the headphone 20. Further, the
ventilation hole 369 for spatially connecting the front-face air
chamber 325 with the rear-face air chamber 332 is provided.
Therefore, in the analysis of the acoustic characteristic of the
headphone 30, there can be used the acoustic equivalent circuit in
consideration of elements generated by the facts that the BA-type
driver units 370 are added to the acoustic equivalent circuit 40 of
FIG. 2, and the ventilation hole 369 is provided in the acoustic
equivalent circuit 40 of FIG. 2. Specifically, the analysis of the
acoustic characteristic of the headphone 30 may be performed by
using the acoustic equivalent circuit in which elements
corresponding to vibratory force, mass, mechanical resistance and
compliance in the BA-type driver units 370, a resistance element by
the ventilation resistance body 323 provided in the ventilation
hole 369, and the like are added to the acoustic equivalent circuit
40 of FIG. 2. Also in the acoustic equivalent circuit of the
headphone 30, formed is the parallel resonance circuit generating
the anti-resonance by the capacitor Cb of the driver-unit rear-face
air chamber 318 and the inductance Mb of the acoustic tube 350.
Therefore, in the acoustic equivalent circuit of the headphone 30,
when a shape of the acoustic tube 350 is optionally set so that the
resonance frequency of the anti-resonance by the capacitor Cb and
the inductance Mb is located in the predetermined frequency band,
it is possible to improve the acoustic characteristic of the
headphone 30.
<5. Complement>
[0138] The preferred embodiment(s) of the present disclosure
has/have been described above with reference to the accompanying
drawings, whilst the present disclosure is not limited to the above
examples. A person skilled in the art may find various alterations
and modifications within the scope of the appended claims, and it
should be understood that they will naturally come under the
technical scope of the present disclosure.
[0139] For example, the case where the headphone according to the
present embodiment is a canal-type earphone has been described
above as an example, but the technology of the present disclosure
is not limited thereto. The headphone according to the present
embodiment may be a headphone of another type. For example, the
headphone according to the present embodiment may be a so-called
overhead-type headphone having a sealed-type front-face air
chamber. Here, the overhead-type headphone is a headphone including
a pair of housings each accommodating the driver unit provided with
the acoustic tube according to the present embodiment, the pair of
housings being coupled with each other by a support member curved
in an arch shape, the headphone being worn on the head with the
support member so that openings provided in the housings for
outputting sound toward the outside face the ears of a user. The
headphone according to the present embodiment is the overhead-type
headphone, the housing and the driver unit are assumed to be
enlarged compared with the canal-type earphone. In that case, when
a value of each element of the acoustic equivalent circuit is
optionally changed according to a change in the characteristic of
the housing and the driver unit, it is possible to design a shape
of the acoustic tube to improve the acoustic characteristic by the
same method as the method described above.
[0140] Furthermore, in the description above, a member that can be
a resistance component of the ventilation resistance body and the
like is not provided in the acoustic tube according to the present
embodiment, but the technology of the present disclosure is not
limited thereto. In the acoustic tube according to the present
embodiment, the ventilation resistance body acting as a resistance
component to a flow of air within the tube may be provided. When
the ventilation resistance body is provided in the acoustic tube,
and a material and a shape of the ventilation resistance body are
optionally set, it becomes possible to adjust a value of the
resistor Rb2 in the acoustic equivalent circuit of FIG. 2. In this
manner, in the present embodiment, the acoustic characteristic may
be adjusted by the ventilation resistance body provided in the
acoustic tube.
[0141] Here, a shape of the housing can be set in consideration of
other elements such as wearability and designability of the
headphone by a user. Further, as described in <4.
Modification> described above, the plurality of driver units and
other structural members can be included within the housing
according to the intended use of the headphone. In the present
embodiment, even when the shape of the housing or the structural
members included in the housing are changed in this manner, it is
possible to design a shape of the acoustic tube by the same method
as the method described above, by optionally changing each element
or its value in the acoustic equivalent circuit according to the
change.
[0142] Additionally, the present technology may also be configured
as below.
(1)
[0143] A headphone including:
[0144] a driver unit that includes a diaphragm;
[0145] a housing that accommodates the driver unit, and forms a
sealed-type front-face air chamber spatially blocked from an
outside except for an opening for sound output on a front face side
provided with the diaphragm of the driver unit; and
[0146] an acoustic tube whose end is directly connected to a first
ventilation hole provided in a frame of the driver unit, and that
spatially connects a driver-unit rear-face air chamber formed
between the frame and the diaphragm with the outside of the driver
unit via a tube.
(2)
[0147] The headphone according to (1),
[0148] wherein, in an acoustic equivalent circuit of the headphone,
a parallel resonance generating anti-resonance at a predetermined
resonance frequency is formed by an acoustic capacitor
corresponding to a capacitance component of the driver-unit
rear-face air chamber, and an acoustic inductance corresponding to
an inductance component of the acoustic tube.
(3)
[0149] The headphone according to (2),
[0150] wherein the resonance frequency is determined at least based
on a value of the acoustic inductance and a value of the acoustic
capacitor.
(4)
[0151] The headphone according to any one of (1) to (3),
[0152] wherein, in the frame of the driver unit, a second
ventilation hole spatially connecting the driver-unit rear-face air
chamber with the outside of the driver unit is provided at a
position different from a position of the first ventilation
hole,
[0153] wherein, in the second ventilation hole, a ventilation
resistance body acting as resistance in the acoustic equivalent
circuit of the headphone is provided, and
[0154] wherein a sound pressure level of the headphone in a
predetermined frequency band is determined at least based on a
value of an acoustic resistor corresponding to a resistance
component of the ventilation resistance body in the acoustic
equivalent circuit.
(5)
[0155] The headphone according to (4),
[0156] wherein the sound pressure level of the headphone in the
predetermined frequency band is determined at least based on the
value of the acoustic capacitor corresponding to the capacitance
component of the driver-unit rear-face air chamber, the value of
the acoustic inductance corresponding to the inductance component
of the acoustic tube in the acoustic equivalent circuit, and the
value of the acoustic resistor.
(6)
[0157] The headphone according to (3),
[0158] wherein the value of the acoustic inductance is determined
according to a length and an inner cross-sectional area of the
acoustic tube, and
[0159] wherein the length and the inner cross-sectional area of the
acoustic tube is set in a manner that the resonance frequency is a
value between 200 (Hz) to 400 (Hz).
(7)
[0160] The headphone according to (6),
[0161] wherein, in the acoustic tube, a ratio of the length to the
inner cross-sectional area is 76 (1/mmm) to 1124 (1/mm).
(8)
[0162] The headphone according to any one of (1) to (7),
[0163] wherein the acoustic tube includes a tubular member formed
of a material having flexibility.
(9)
[0164] The headphone according to (8),
[0165] wherein the frame of the driver unit has a disk shape, and
wherein the tubular material is arranged along a circumference
direction of the disk shape.
(10)
[0166] The headphone according to any one of (1) to (7),
[0167] wherein the acoustic tube is formed by arranging a rod-like
member whose face has a groove formed toward a longitudinal
direction in a manner that the face on which the groove is formed
is closely fitted to one face on a rear face side opposite to the
front face side of the frame of the driver unit, and at least one
part of the groove is in contact with the first ventilation
hole.
(11)
[0168] The headphone according to (10),
[0169] wherein the frame of the driver unit has a disk shape,
and
[0170] wherein the rod-like member is curved in an arch shape to
have curvature equal to or less than a circumference of the
disk-like shape, and arranged along a circumference direction of
the disk-like shape.
(12)
[0171] The headphone according to any one of (1) to (11),
[0172] wherein the driver unit is a dynamic driver unit.
(13)
[0173] The headphone according to (12),
[0174] wherein a balanced armature driver unit is further
accommodated within the housing.
(14)
[0175] The headphone according to any one of (1) to (13),
[0176] wherein the acoustic tube spatially connects the driver-unit
rear-face air chamber with the outside of the housing via the
tube.
(15)
[0177] The headphone according to (14),
[0178] wherein a rear-face air chamber as a space surrounded by the
housing and the driver unit is formed on a rear face side opposite
to the front face side of the driver unit,
[0179] wherein an opening spatially connecting the rear-face air
chamber with the outside of the housing is provided in the housing,
and
[0180] wherein the other end of the acoustic tube is provided
within the rear-face air chamber.
(16)
[0181] The headphone according to (14),
[0182] wherein the other end of the acoustic tube is provided in
the outside of the housing.
(17)
[0183] The headphone according to any one of (1) to (16),
[0184] wherein a sound guiding tube as a tubular part projecting
toward the outside is formed in one part of a region constituting
the front-face air chamber of the housing,
[0185] wherein the opening for sound output is provided in a tip
end part of the sound guiding tube, and
[0186] wherein the headphone is a canal-type earphone in which the
tip end part of the sound guiding tube is inserted into an external
auditory canal of a user.
(18)
[0187] The headphone according to any one of (1) to (17),
[0188] wherein the headphone includes a pair of the housings that
accommodate the driver unit,
[0189] wherein the pair of the housings are coupled with each other
by a support member curved in an arch shape, and
[0190] wherein the headphone is an overhead-type headphone worn on
a head of a user with the support member in a manner that the
opening for sound output of the housing faces an ear of the
user.
(19)
[0191] An acoustic characteristic adjusting method including:
[0192] accommodating a driver unit that includes a diaphragm within
a hosing, and forming a sealed-type front-face air chamber
spatially blocked from an outside except for an opening for sound
output, between the housing and a front face side provided with the
diaphragm of the driver unit; and
[0193] providing an acoustic tube whose end is directly connected
to a first ventilation hole provided in a frame of the driver unit,
and that spatially connects a driver-unit rear-face air chamber
formed between the frame and the diaphragm with the outside of the
driver unit via a tube.
REFERENCE SIGNS LIST
[0194] 10, 20, 30 headphone [0195] 40 acoustic equivalent circuit
[0196] 110, 210 driver unit [0197] 111, 211, 311 frame [0198] 116a,
116b, 116c, 216a, 216b, 316a, 316b ventilation hole [0199] 117a,
117b, 217a, 317a ventilation resistance body [0200] 118, 218, 318
driver-unit rear-face air chamber [0201] 120 front housing [0202]
121, 221, 361 opening [0203] 125 front-face air chamber [0204] 130
rear housing [0205] 132 rear-face air chamber [0206] 140 housing
[0207] 310 dynamic-type driver unit [0208] 360 middle housing
[0209] 370 balanced armature-type driver unit (BA-type driver
unit)
* * * * *